Association between childhood maltreatment with subthreshold depressive symptoms and major depressive disorder in young and middle-aged adults

Abstract

BACKGROUND

Childhood maltreatment has a potentially lasting influence on subthreshold depressive symptoms (SDS) and major depressive disorder (MDD). This study aimed to explore the association of childhood maltreatment with MDD and SDS, focusing on the differences between young and middle-aged adults.

AIM

To examine the associations among childhood maltreatment, SDS, and MDD in young and middle-aged adults.

METHODS

A total of 3209 adults were recruited from 34 primary healthcare settings. The Childhood Trauma Questionnaire-28 item Short Form was used to assess childhood maltreatment. The Patient Health Questionnaire-9 was used to assess SDS and the Mini-International Neuropsychiatric Interview depression module was used to assess MDD.

RESULTS

Childhood maltreatment was significantly associated with higher odds of developing SDS and MDD than in the non-depressed control group (P < 0.05). Childhood maltreatment significantly increased the risk of developing SDS in young adults but was not significantly associated with SDS in middle-aged adults (P = 0.055). Conversely, childhood maltreatment was significantly associated with MDD in both young (P < 0.001) and middle-aged adults (P < 0.05). In young adults, various types of childhood maltreatment were associated with MDD; however, only emotional abuse and neglect were significantly associated with MDD in middle-aged adults.

CONCLUSION

Our study revealed a strong association among childhood maltreatment, SDS, and MDD across age groups, highlighting the impact of emotional abuse and need for trauma-informed depression care.

Key Words: Subthreshold depressive symptoms; Major depressive disorder; Childhood maltreatment; Adults

Core Tip: This study investigates the association between childhood maltreatment and both subthreshold depressive symptoms (SDS) and major depressive disorder (MDD) in young and middle-aged adults. Our findings reveal that emotional abuse and neglect significantly contribute to depression risk across age groups, with emotional neglect showing a particularly strong association. This study extends previous literature by differentiating between SDS and MDD and underscores the need for trauma-informed care in depression management. Early identification of childhood maltreatment is crucial for preventing depression in at-risk individuals.

INTRODUCTION

Major depressive disorder (MDD) is a mood disorder characterized by persistent and severe feelings of sadness, hopelessness, and loss of interest or pleasure in daily activities[1]. It constitutes a significant global health burden, and the advent of the coronavirus disease 2019 (COVID-19) pandemic has exacerbated mental health issues[2]. In China, depressive disorders are estimated as the second leading cause of years lived with disability[3]. Subthreshold depressive symptoms (SDS) refer to mild depressive symptoms that do not meet the diagnostic criteria for clinical depression but still have a negative impact on an individual’s health-related quality of life and mental health[4]. SDS is significant as it is likely to be underestimated or overlooked. Specifically, individuals experiencing these symptoms may mistakenly perceive them as mood fluctuations or typical aspects of everyday life, resulting in delays in obtaining vital assistance and support[5]. If not addressed promptly, SDS may gradually develop into more severe MDD, ultimately increasing both the complexity and cost of treatment[6].

Childhood adversity has drawn increasing attention in the understanding of the causes of depressive symptoms. Childhood maltreatment is a major public health problem worldwide, with serious and often debilitating long-term consequences for psychosocial development as well as depression[7,8]. Even in high-income countries, about 4%-16% of children are physically abused, and 10% are subjected to neglect or psychological abuse annually[9]. Global prevalence estimates indicate that child physical abuse (8.0%), sexual abuse (1.6%), emotional abuse (36.3%) and neglect (4.4%) are common forms of childhood maltreatment[10,11]. Prior studies have estimated that 59% of depression cases worldwide can be attributed to childhood maltreatment, and that a 10% reduction in childhood maltreatment can prevent 310000 cases of depression[12]. However, further research is required to examine the unique long-term effects of different types of childhood maltreatment. Children who suffer from emotional abuse and neglect may develop negative self-cognition patterns and have difficulty regulating emotions, which are related to the pathogenesis of depression[13,14]. Complex Trauma usually begins in early childhood and involves ongoing adverse experiences caused by others, often within crucial attachment relationships. It is sometimes worsened by patterns of risk and family dysfunction across generations. Thus, exploring the association of different types of childhood maltreatment with both SDS and MDD is essential to gain a comprehensive understanding of their varying impacts on mental health.

The risk of internalizing disorders in childhood maltreatment victims continues into adulthood, and the role of childhood abuse in the etiology and maintenance of depression has been repeatedly demonstrated in community studies[15]. However, the duration of the effects of abuse maintenance is a complex issue[16], and few studies have discussed whether childhood maltreatment affects people of different ages. Previous studies have seldom conducted further breakdowns of adult individuals into distinct age groups, as the severity of childhood abuse can vary among individuals of different ages[17]. Adults aged 18-44 are commonly defined as young, and those aged 45-59 as middle-aged, according to prior demographic and psychological literature, combined with China’s classification of old age as beginning at 60 years[18-20]. This age distinction is particularly relevant in the Chinese context, where different cohorts have grown up under distinct historical and policy environments. For example, the One-Child Policy (1980-2015) reshaped family structures by concentrating parental expectations on a single child, often resulting in authoritarian parenting, increased psychological pressure, or diminished emotional responsiveness, thereby elevating the risk of emotional maltreatment[21]. Rapid socioeconomic transitions during China's reform and opening-up period may have disrupted traditional caregiving practices and introduced intergenerational stress within families. These historical and cultural factors likely contributed to variations in the type, prevalence, and severity of childhood maltreatment reported across different age cohorts[22-24].

Furthermore, as individuals age, their psychological and physiological developments continuously change. Childhood maltreatment may have lasting effects on an individual’s mental wellbeing, but these effects can vary with age[25]. Individuals of different age groups may exhibit different coping strategies, emotion regulation abilities, and social support preferences, all of which could modulate the association between childhood maltreatment and depression[26]. Previous studies on depression have often lacked detailed analyses of different age groups, ignoring possible differences in the effects of different psychological and life stages, potentially masking the specific consequences and mechanisms that may be at play at distinct ages.

Accordingly, the following three research questions were proposed: (1) Is childhood maltreatment associated with SDS and MDD in adults? (2) Are there differences in these associations between young and middle-aged adults? and (3) Which specific types of childhood maltreatment are most strongly associated with depressive outcomes across different age groups?

Therefore, by stratifying the population according to age groups, our study aimed to investigate the effects of childhood maltreatment on SDS and MDD in individuals of different ages, thereby providing more profound insights into the development of age-specific intervention strategies.

MATERIALS AND METHODS

Study design

Our study was conducted using data from the Chinese Depression Cohort (DCC) Study (ChiCTR registration number 1900022145), an ongoing longitudinal population-based investigation focusing on the early identification, treatment, prevention, and management of SDS and MDD. Employing the Building Bridges integrated Care (Bridges) model, the DCC study aligns with Shenzhen’s healthcare system by linking primary care centers, specialist hospitals, and community care. Screening was conducted in two communities, 34 primary care centers, a general hospital, and a mental health specialty hospital in Shenzhen, China. We recruited participants aged 18-65 who met the SDS and MDD criteria between March 2019 and March 2023. Ethical approval was obtained from the Institutional Review Board of the Sun Yat-sen University School of Public Health (Ethical code: L2017044), and the study protocol was approved by the Ethical Review Boards of all participating centers in accordance with the Declaration of Helsinki.

Participants

The study recruited participants from Shenzhen’s Nanshan District using a consecutive sampling strategy at 34 primary care centers and one psychiatric hospital. Approximately 90000 community residents attend these centers annually. Starting in early 2019, general physicians (GPs) screened patients during routine clinical visits, focusing on individuals presenting with mental health-related physical symptoms (e.g., chronic somatic pain, insomnia) or those perceived as having a higher likelihood of mental health issues based on GPs’ clinical expertise and standardized study training. This sampling approach aimed to reflect the real-world clinical population visiting urban community clinics, rather than a strictly random or population-representative sample. The Patient Health Questionnaire-9 (PHQ-9) questionnaire was used to identify individuals with depressive symptoms. For those screened positive for depressive symptoms through the PHQ-9, the Mini-International Neuropsychiatric Interview (M.I.N.I.), a structured and validated diagnostic tool aligned with the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition Text Revision criteria, was administered by a GP to identify SDS and MDD. Following assessment, participants newly considered to have MDD were referred to psychiatric service institutions for additional evaluation. Exclusion criteria for SDS and MDD were as follows: (1) A DSM-5 diagnosis of severe mental disorder and/or alcohol or drug addiction disorder; (2) Pregnant or perinatal women; (3) Not fluent in Mandarin; and (4) Inability to understand research questionnaires or provide informed consent. Written informed consent was obtained from all participants after they were fully informed of the study protocol. Individuals aged 18-44 years were classified as young adults, while those aged 45-59 years fall into the category as middle-aged adults[20,27]. A total of 3209 individuals volunteered to complete the screening.

Outcome measures

Assessment of childhood maltreatment: Childhood maltreatment was evaluated using the Chinese version of the Childhood Trauma Questionnaire-28 item Short Form (CTQ-SF). The CTQ-SF is a frequently used tool for assessing early traumatic experiences with good reliability and high internal consistency (Cronbach’s alpha = 0.84). The CTQ-SF has five subscales covering five types of childhood maltreatment: Physical abuse (items 9, 11, 12, 15, 17), emotional abuse (items 3, 8, 14, 18, 25); sexual abuse (items 20, 21, 23, 24, 27); physical neglect (items 1, 2, 4, 6, 26); and emotional neglect (items 5, 7, 13, 19, 28). The responses to items 10, 16, and 22 were utilized to assess the questionnaire’s construct and criterion validity and were not included in the calculation of the total score. Each subscale consisted of five questions about childhood experiences. The responses are rated on a 5-point scale (“1 = never”, “2 = rarely”, “3 = sometimes”, “4 = often”, and “very often = 5”), the total of scores range from 25 to 125, and subscale scores range from 5 to 25. Higher subscale scores indicate more severe childhood maltreatment experiences. Before administering the CTQ-SF, trained mental health professionals provided the participants with a standardized explanation of the questionnaire, emphasizing the sensitive nature of its content and the voluntary nature of participation. Participants were assured of full confidentiality and all responses were anonymized and stored on secure password-protected servers. The explanation also included their right to skip any questions or withdraw from the study at any time, without incurring penalties.

Evaluation of SDS and MDD

SDS were evaluated by GPs through the PHQ-9, a widely validated instrument for assessing depressive symptoms, with a Cronbach’s alpha of 0.80 observed in our sample. The PHQ-9 includes nine items assessing depressive symptoms over the past two weeks, rated from 0 (“not at all”) to 3 (“nearly every day”). Elevated total scores reflect greater severity of depressive symptoms, with a maximum attainable score of 27. SDS in this study was defined as PHQ-9 ≥ 5 without any diagnosis of MDD, confirmed via the M.I.N.I.

Higher PHQ-9 scores indicate greater risk of MDD. For instance, a PHQ-9 score of 10 or above is considered a strong indicator of MDD. Accordingly, individuals meeting this threshold were directed to the psychiatric department for an in-person assessment using the M.I.N.I. Although the depression module was used for identifying MDD, trained clinicians simultaneously assessed other modules to exclude alternative psychiatric diagnoses, in accordance with the M.I.N.I. structured protocol. The M.I.N.I., a validated diagnostic psychiatric interview, exhibits robust psychometric properties and serves as the gold standard in clinical research on MDD diagnosis[28].

Covariates

Additional covariates were assessed using self-administered questionnaires. The demographic variables included age, gender, education, marital status, family income, employed status, health status and behavioral characteristics including smoking, drinking, chronic disease, and weekly exercise habits (at least once a week and ≥ 30 min) were collected. Chronic disease was classified by the reported presence of one or more physician-diagnosed conditions, including: (1) Hypertension; (2) Apoplexy; (3) Diabetes; (4) Cardiovascular disorders; (5) Thyroid dysfunction; (6) A prior diagnosis of cancer, and (7) Mental illness. Smoking was assessed by asking the following question: “Have you ever smoked?” Drinking was assessed by asking the following question: “Have you had at least one alcoholic drink?”

Statistical analysis

Descriptive statistical methods were employed to characterize participant sociodemographic features and to compute group-wise mean scores for each subtype of childhood maltreatment, as detailed in Table 1. Continuous data were analyzed using the t-test and reported as mean and SD, whereas categorical data were analyzed using the χ² test and reported as frequencies and percentages. Second, the average score of each type of childhood maltreatment were calculated and compared based on young and middle-aged adults by SDS and MDD groups (Table 2). To assess the association between childhood maltreatment and depressive outcomes, multivariable multinomial logistic regression analyses were performed (Table 3), with adjustments for sex, age, marital status, education, employment status, family income, chronic disease, drinking, smoking, and weekly exercise habits. The resulting β coefficients and 95%CI were calculated to quantify the strength and precision of these associations. Third, logistic regression was used to compare the associations of different types of childhood maltreatment with SDS and MDD in young and middle-aged adults after adjusting for sex, marital status, education, employment status, family income, chronic disease, smoking, drinking, and weekly exercise habits (Tables 4 and 5). All analyses were conducted using Stata version 25.0 (IBM Corp., Armonk, NY, United States). All statistical tests were two-sided, with significance defined as P < 0.05.

Table 1 Characteristics of the study participants, n (%).

	Overall (n = 3209)	Non-depressed (n = 143)	SDS (n = 1524)	MDD (n = 1542)	P value1
Demographic characteristics
Age (years)2	33.6 ± 10.2	37.2 ± 10.4	38.5 ± 10.1	28.4 ± 7.4	< 0.001
Age group					< 0.001
18-44 years	2680 (83.5)	110 (76.9)	1096 (71.9)	1474 (95.6)
45-59 years	529 (16.5)	33 (23.1)	428 (28.1)	68 (4.4)
Gender					< 0.001
Male	1089 (34.0)	34 (23.8)	583 (38.3)	472 (30.6)
Female	2118 (66.0)	109 (76.2)	939 (61.7)	1070 (69.4)
Missing data	2	0	2	0
Marital status					< 0.001
Single	1498 (47.1)	49 (34.3)	449 (29.5)	1000 (66.0)
Married	1541 (48.5)	89 (62.2)	1017 (66.9)	435 (28.7)
Divorce/widowed	139 (4.4)	5 (3.5)	54 (3.6)	80 (5.3)
Missing data	31	0	4	27
Education					< 0.001
Below undergraduate	1574 (49.2)	72 (50.3)	826 (54.5)	676 (43.9)
Undergraduate or above	1624 (50.8)	71 (49.7)	691 (45.5)	862 (56.1)
Missing data	11	0	7	4
Employed status					0.050
Employed	2667 (83.4)	114 (79.7)	1290 (85.0)	1263 (82.2)
Un-employed	530 (16.6)	29 (20.3)	227 (15.0)	274 (17.8)
Missing data	12	0	7	5
Family income					< 0.001
< 20000¥	2205 (71.1)	119 (83.2)	1134 (74.7)	952 (66.0)
≥ 20000¥	898 (28.9)	24 (16.8)	383 (25.3)	491 (34.0)
Missing data	106	0	7	99
Health status and behavioral habits
Chronic disease					< 0.001
No	899 (28.1)	27 (18.9)	381 (25.0)	491 (32.1)
Yes	2299 (71.9)	116 (81.1)	1143 (75.0)	1040 (67.9)
Missing data	11	0	0	11
Smoking					< 0.001
No	1099 (34.4)	27 (18.9)	418 (27.5)	654 (42.6)
Yes	2100 (65.6)	116 (81.1)	1104 (72.5)	880 (57.4)
Missing data	10	0	2	8
Drinking					< 0.001
No	2374 (74.1)	84 (58.7)	975 (64.1)	1315 (85.5)
Yes	829 (25.9)	59 (41.3)	547 (35.9)	223 (14.5)
Missing data	6	0	2	4
Exercise habit per week (at least 1 time and ≥ 30 minutes)					< 0.001
No	2060 (64.5)	84 (59.2)	867 (57.0)	1109 (72.3)
Yes	1135 (35.5)	58 (40.8)	653 (43.0)	424 (27.7)
Missing data	14	1	4	9
PHQ-9	13.1 ± 7.3	1.6 ± 1.4	8.7 ± 4.5	18.4 ± 5.5	< 0.001

¹T-tests were used for continuous variables.

²Data are presented as the mean ± SD.

χ² tests were used for categorical variables. SDS: Subthreshold depressive symptoms; MDD: Major depressive disorder; PHQ-9: Patient Health Quetionaire-9.

Table 2 The average scores of different types of childhood maltreatment in young and middle-aged adults by subthreshold depressive symptoms and major depressive disorder groups.

Variables	Young adults (18-44 years old) (n = 2680)	Middle-aged adults (45-59 years old) (n = 529)	P value
CTQ-SF total score	44.7 ± 14.0	39.1 ± 11.4	< 0.001
Non-depressed	36.1 ± 9.8	35.5 ± 8.6	0.769
SDS	41.7 ± 13.4	39.0 ± 11.5	< 0.05
MDD	47.6 ± 14.1	41.2 ± 11.7	< 0.05
CTQ-SF scores for physical abuse	6.5 ± 2.9	5.8 ± 2.0	< 0.001
Non-depressed	5.3 ± 0.9	5.4 ± 1.2	0.486
SDS	6.1 ± 2.6	5.8 ± 2.0	< 0.05
MDD	6.9 ± 3.2	6.0 ± 2.3	< 0.05
CTQ-SF scores for emotional abuse	8.7 ± 4.4	6.5 ± 2.5	< 0.001
Non-depressed	6.1 ± 1.9	5.7 ± 1.4	0.252
SDS	7.4 ± 3.5	6.5 ± 2.4	< 0.001
MDD	9.9 ± 4.7	7.3 ± 3.1	< 0.001
CTQ-SF scores for sexual abuse	5.7 ± 1.9	5.5 ± 1.6	< 0.05
Non-depressed	5.3 ± 1.0	5.2 ± 0.9	0.821
SDS	5.7 ± 2.0	5.5 ± 1.7	0.071
MDD	5.7 ± 1.8	5.6 ± 1.2	0.507
CTQ-SF scores for physical neglect	9.6 ± 3.8	9.5 ± 3.4	0.394
Non-depressed	8.1 ± 3.1	9.0 ± 3.0	0.181
SDS	9.5 ± 3.7	9.5 ± 3.4	0.845
MDD	9,8 ± 3.8	9.5 ± 3.5	0.561
CTQ-SF scores for emotional neglect	14.2 ± 5.9	11.8 ± 5.5	< 0.001
Non-depressed	11.3 ± 6.3	10.2 ± 4.9	0.375
SDS	12.9 ± 6.1	11.7 ± 5.6	< 0.05
MDD	15.3 ± 5.4	12.8 ± 5.4	< 0.05

SDS: Subthreshold depressive symptoms; MDD: Major depressive disorder; CTQ-SF: Childhood Trauma Questionnaire-28 item Short Form.

Table 3 Univariate and multivariate analysis of association between different types of childhood maltreatment and subthreshold depressive symptoms or major depressive disorder.

Variables	SDS		MDD		SDS		MDD
	OR (95%CI)1	P value	OR (95%CI)1	P value	AOR (95%CI)2	P value	AOR (95%CI)2	P value
CTQ-SF	1.04 (1.03, 1.06)	< 0.001	1.08 (1.06, 1.10)	< 0.001	1.05 (1.03, 1.07)	< 0.001	1.07 (1.05, 1.09)	< 0.001
Physical abuse	1.49 (1.22, 1.82)	< 0.001	1.66 (1.36, 2.03)	< 0.001	1.41 (1.16, 1.71)	< 0.05	1.48 (1.22, 1.79)	0.001
Emotional abuse	1.24 (1.13, 1.36)	< 0.001	1.47 (1.33, 1.62)	< 0.001	1.28 (1.13, 1.44)	< 0.001	1.41 (1.24, 1.59)	< 0.001
Sexual abuse	1.28 (1.05, 1.56)	< 0.05	1.30 (1.07, 1.58)	< 0.05	1.26 (1.05, 1.52)	< 0.05	1.22 (1.01, 1.48)	< 0.05
Physical neglect	1.11 (1.05, 1.17)	< 0.001	1.13 (1.07, 1.19)	< 0.001	1.11 (1.05, 1.18)	< 0.001	1.13 (1.06, 1.19)	< 0.001
Emotional neglect	1.05 (1.02, 1.09)	< 0.05	1.14 (1.10, 1.17)	< 0.001	1.06 (1.02, 1.09)	< 0.05	1.11 (1.08, 1.15)	< 0.001

¹Univariate model.

²Adjusted for sex, age, marital status, education, employed status, family income, chronic disease, smoking, drinking, exercise habit per week.

SDS: Subthreshold depressive symptoms; MDD: Major depressive disorder; CTQ-SF: Childhood Trauma Questionnaire-28 item Short Form.

Table 4 Association between different types of childhood maltreatment with subthreshold depressive symptoms in young and middle-aged adults.

Variables	Young adults (18-44 years old) (n = 2680)				Middle-aged adults (45-59 years old) (n = 529)
	OR (95%CI)1	P value	AOR (95%CI)2	P value	OR (95%CI)1	P value	AOR (95%CI)2	P value
CTQ-SF	1.04 (1.03, 1.07)	< 0.001	1.05 (1.03, 1.07)	< 0.001	1.03 (0.99, 1.07)	0.089	1.04 (0.99, 1.08)	0.055
Physical abuse	1.64 (1.27, 2.11)	< 0.001	1.57 (1.22, 2.02)	< 0.001	1.17 (0.88, 1.54)	0.282	1.12 (0.86, 1.47)	0.396
Emotional abuse	1.25 (1.12, 1.39)	< 0.001	1.25 (1.12, 1.39)	< 0.001	1.24 (0.97, 1.59)	0.083	1.26 (0.98, 1.62)	0.073
Sexual abuse	1.30 (1.04, 1.62)	< 0.05	1.28 (1.03, 1.59)	< 0.05	1.21 (0.82, 1.79)	0.336	1.18 (0.81, 1.71)	0.383
Physical neglect	1.13 (1.06, 1.20)	< 0.001	1.12 (1.05, 1.20)	< 0.001	1.05 (0.94, 1.17)	0.379	1.07 (0.96, 1.21)	0.216
Emotional neglect	1.05 (1.02, 1.09)	< 0.05	1.05 (1.01, 1.09)	< 0.05	1.06 (0.98, 1.14)	0.132	1.07 (0.99, 1.15)	0.075

¹Univariate model.

²Adjusted for sex, marital status, education, employed status, family income, chronic disease, smoking, drinking, exercise habit per week.

CTQ-SF: Childhood Trauma Questionnaire-28 item Short Form.

Table 5 Association between different types of childhood maltreatment with major depressive disorder in young and middle-aged adults.

Variables	Young adults (18-44 years old) (n = 2680)				Middle-aged adults (45-59 years old) (n = 529)
	OR (95%CI)1	P value	AOR (95%CI)2	P value	OR (95%CI)1	P value	AOR (95%CI)2	P value
CTQ-SF	1.08 (1.06, 1.11)	< 0.001	1.08 (1.05, 1.10)	< 0.001	1.05 (1.01, 1.09)	< 0.05	1.05 (1.01, 1.10)	< 0.05
Physical abuse	1.80 (1.40, 2.33)	< 0.001	1.68 (1.31, 2.16)	< 0.001	1.22 (0.91, 1.64)	0.181	1.17 (0.88, 1.57)	0.280
Emotional abuse	1.45 (1.31, 1.61)	< 0.001	1.41 (1.27, 1.56)	< 0.001	1.38 (1.07, 1.78)	< 0.05	1.33 (1.02, 1.73)	< 0.05
Sexual abuse	1.30 (1.05, 1.63)	< 0.05	1.25 (1.01, 1.55)	< 0.05	1.24 (0.82, 1.87)	0.306	1.18 (0.79, 1.77)	0.426
Physical neglect	1.15 (1.08, 1.22)	< 0.001	1.15 (1.08, 1.22)	< 0.001	1.05 (0.93, 1.19)	0.442	1.07 (0.93, 1.22)	0.348
Emotional neglect	1.13 (1.09, 1.18)	< 0.001	1.12 (1.08, 1.17)	< 0.001	1.09 (1.01, 1.19)	< 0.05	1.09 (1.01, 1.19)	< 0.05

¹Univariate model.

²Adjusted for sex, marital status, education, employed status, family income, chronic disease, smoking, drinking, exercise habit per week.

CTQ-SF: Childhood Trauma Questionnaire-28 item Short Form.

RESULTS

Descriptive statistics of participant characteristics

Demographic characteristics of the 3209 participants are summarized in Table 1, with 34.0% male and 66.0% female. The mean ± SD age was 33.6 (± 10.2) years, and the age of participants spanned from 18 to 59 years. In total, 143 participants (4.5%) were categorized as non-depressed controls, while 1524 (47.5%) were identified with SDS, and 1542 (48.0%) met criteria for MDD. Employment status appeared similar across all groups. Compared with the control group, individuals in both the SDS and MDD groups were significantly more likely to be female (P < 0.05) and to report being single, divorced, or widowed (P < 0.001). Participants experiencing SDS or MDD also reported higher prevalence of smoking, drinking, chronic diseases, and reduced engagement in regular physical activity.

The average scores of different types of childhood maltreatment in different groups

As shown in Table 2, the total scores of CTQ-SF were higher in young adults (44.7 ± 14.0) compared to middle-aged adults (39.1 ± 11.4) (P < 0.001). The difference in total scores of CTQ-SF between non-depressed young adults (36.1 ± 9.8) and non-depressed middle-aged adults (35.5 ± 8.6) was not statistically significant (P = 0.769), with young adults having higher Childhood Trauma Questionnaire (CTQ) total scores than middle-aged adults among persons living with SDS and MDD (P < 0.001). The scores for emotional neglect, emotional abuse, and physical abuse of young adults living with SDS and MDD were significantly higher than those of middle-aged adults living with SDS and MDD (P < 0.001). However, there were no significant differences in the scores for sexual abuse and physical neglect between the young and middle-aged adults.

The association between different types of childhood maltreatment and SDS/ MDD

As presented in Table 3, after adjusting for sex, age, education, marital status, employment status, chronic disease, family income, smoking, drinking, weekly exercise habit (model 2), the total score of CTQ-SF was significant for the SDS (AOR = 1.05, 95%CI: 1.03-1.07) and MDD groups (AOR = 1.07, 95%CI: 1.05-1.09).

For individuals living with SDS without adjusting for other variables (unadjusted model), the five subscales were positively related to SDS (P < 0.05). Moreover, the association between physical and emotional abuse and SDS was stronger than with other types of childhood maltreatment. After adjusting for sex, age, education, marital status, employment status, chronic disease, family income, smoking, drinking, and weekly exercise habits (adjusted model 2), different types of childhood maltreatment, including physical abuse, emotional abuse, sexual abuse, physical neglect, and emotional neglect, were associated with an elevated risk of SDS when compared to non-depressed individuals.

For individuals living with MDD, without adjusting for other variables (unadjusted model), the five subscales were positively related to MDD (P < 0.05). Moreover, the association between physical and emotional abuse and MDD was stronger than with other types of childhood maltreatment. After adjusting for the same variables as in the SDS model (adjusted model 2), different types of childhood maltreatment were associated with an elevated risk of MDD compared to non-depressed individuals. The AOR for physical abuse, emotional abuse, sexual abuse, physical neglect, and emotional neglect were greater in the MDD group than the SDS group.

Association between different types of childhood maltreatment with SDS or MDD in young and middle-aged adults

As shown in Table 4, after adjusting for variables, the total CTQ-SF scores and five types of childhood maltreatment were associated with SDS in young adults [AOR = 1.05 (1.03, 1.07)], with physical abuse having the strongest association with SDS [AOR = 1.57 (1.22, 2.02)]. Notably, there was no statistically significant association between childhood maltreatment and SDS scores in middle-aged adults (P = 0.055). As shown in Table 5, the total scores for childhood maltreatment in both young [AOR = 1.08 (1.05, 1.10)] and middle-aged adults [AOR = 1.05 (1.01, 1.10)] were associated with MDD. In young adults, all five types of childhood maltreatment were associated with MDD (P < 0.05), with physical abuse [AOR = 1.68 (1.31, 2.16)] and emotional abuse [AOR = 1.41 (1.27, 1.56)] having the strongest association. However, in middle-aged adults, only emotional abuse [AOR = 1.33 (1.02, 1.73)] and emotional neglect [AOR = 1.09 (1.01, 1.19)] were associated with MDD.

DISCUSSION

In this study, we observed higher scores for emotional neglect, physical abuse, and emotional abuse among young adults than middle-aged adults with SDS and MDD. However, no statistically significant differences were observed between sexual abuse and physical neglect in the sample groups. In both age groups, individuals who had experienced emotional neglect had the highest scores for childhood maltreatment. Second, different types of childhood maltreatment were significantly associated with the likelihood of having SDS or MDD compared with the non-depressed control group. Third, childhood maltreatment increased the risk of developing SDS in young adults; however, no significant association was found among middle-aged adults. Childhood maltreatment was significantly associated with MDD in both young and middle-aged adults. In young adults, various types of childhood maltreatment were associated with MDD, whereas in middle-aged adults, only emotional abuse and neglect were significantly associated with MDD.

Our findings extend existing research by providing further evidence that individuals living with SDS/MDD, who have higher scores for emotional neglect, emotional abuse, and physical abuse in different types of childhood maltreatment than non-depressed individuals[29,30]. Notably, young adults obtained higher scores on these three dimensions of childhood maltreatment than did middle-aged adults in our study. This trend may reflect generational changes in China, with younger adults showing greater openness to disclosing abuse as societal attitudes toward mental health and trauma have become more accepting[24,31]. However, it is important to note that the lower scores observed in middle-aged adults are more likely due to culturally influenced underreporting and generational norms of emotional restraint rather than simple recall bias. Furthermore, no significant differences in sexual abuse and physical neglect were observed between the two age groups. This may be due to cultural taboos and stigma surrounding sexual abuse, particularly among older Chinese adults, where concerns about family reputation and social norms are likely to contribute to underreporting[32]. Physical neglect, as a more passive form of maltreatment, may be subject to greater underreporting because of its less overt nature compared to active physical or emotional abuse[13]. Additionally, passive forms of maltreatment, such as neglect, may be subject to greater recall bias, particularly over longer periods of time[33]. Notably, emotional neglect had the highest scores in childhood maltreatment across both age groups. This suggests that emotional neglect plays a significant role in the development of MDD[34]. The enduring effects of emotional neglect may affect self-identity, emotional regulation, and mental health. It is crucial to consider these factors when treating individuals, particularly those who have experienced emotional neglect. Therefore, when managing these patients, it is important to prioritize their childhood experiences of emotional neglect and incorporate interventions aimed at addressing the psychological trauma stemming from these experiences[35].

Adults who experience abuse or neglect in childhood are not only at higher risk for a range of externalizing problems[36,37], but they are also at a higher risk for internalizing problems with a range of adverse mental health outcomes, including depression[38]. There are multiple potential mechanisms by which maltreatment increases the pathological risk of depression, from epigenetic processes and gene expression to neuroendocrine, immune, and neurotransmitter systems, brain structure and function, and social cognition[17,34]. One possible explanation that has been hypothesized is a diminished response to rewards from experiencing childhood abuse; this is hypothesized to be a neurological mechanism by which abuse increases the risk of depression, specifically anhedonia symptoms[39]. Behaviorally, adults who were abused as children were less sensitive to reward cues than non-abused controls. The mesencephalic limbic dopa intestinal circuit, which projects into the basal ganglia (including the ventral striatum and nucleus accumbens), is involved in the response to rewards, especially the anticipation of rewards[40]. Thus, in tasks that presented participants with reward, loss, and non-incentive cues, young people who had been abused during childhood rated reward cues less positively than others[40]. Regarding genetic factors, there is evidence that genotype-abuse (G × E) interactions may be associated with depression. Individuals carrying the 5-HTTLPR S allele may have an elevated risk of depression because they have a more pronounced physiological response to stress than carriers of the L allele[41,42].

Furthermore, adults with a history of childhood abuse tend to receive lower levels of social support from friends and family[43] and less stable social support throughout their lives[44]. One key process affected by childhood maltreatment is the children’s ability to establish secure and lasting relationships with caregivers[45]. Childhood maltreatment is closely related to insecure attachment, which is associated with a wide range of social interpersonal problems in adulthood, including disclosure, social support, and acknowledgment[46]. In addition to individual differences in the development of reward-related neural circuits associated with early life stress, cultural and generational differences in how individuals are taught to express and report emotions may also contribute to variations in depressive outcomes across age groups[47]. Specifically, we found that childhood maltreatment was significantly associated with SDS in young but not in middle-aged adults. One possible explanation is that younger adults are still navigating transitional life stages, such as higher education, early careers, or forming relationships, and may be more vulnerable to unresolved trauma that manifests as subthreshold symptoms[48]. By contrast, middle-aged adults may have developed coping strategies or presented more overt depressive symptoms, thereby reducing the detectability of SDS in this group.

Our findings also underscore the important role of emotional abuse and neglect in childhood in the long-term adverse effects of MDD in young and middle-aged adults. Emotional abuse and neglect may often manifest as hidden forms of harm lacking the obvious physical evidence observed in cases of childhood physical and sexual abuse. This covert nature can render it challenging for victims to articulate and disclose their experiences while also making detection and intervention by society more arduous[49]. Consequently, these experiences may persist untreated, causing harm. Moreover, emotional abuse can erode self-esteem, self-worth, and self-identity. This psychological damage can persist into adulthood and contribute to the development of depression[50]. This conclusion underscores the importance of emotional trauma and the need for tailored interventions and prevention strategies.

Our study has methodological limitations that affect the inference and interpretation of our data. First, we relied on self-reported measures to assess childhood maltreatment, which may have introduced recall bias owing to the retrospective nature of the study. Second, as a cross-sectional study, causal inferences cannot be made, and further prospective research is needed to explore the risk factors and longitudinal effects in individuals with SDS and MDD. Third, our results are based on populations in the economically developed city of Shenzhen, which may limit the generalizability of the findings, as evidence suggests that individuals in socioeconomically and educationally disadvantaged areas face greater risk of childhood abuse[9]. Fourth, middle-aged individuals recollect childhood experiences more distantly than young adults do, which may lead to an increased recall bias in middle-aged participants, potentially weakening the observed association between childhood maltreatment and SDS and MDD. Fifth, the data collection during the COVID-19 pandemic may have exacerbated depressive symptoms, potentially inflating the observed associations with childhood maltreatment[51,52]. Sixth, the small size of the non-depressed control group due to symptom-based recruitment may have introduced a selection bias and limited group comparability. Finally, there may be a potential for selection bias arising from the separate investigations of two distinct age groups (young and middle-aged adults), which could introduce confounding variables and limit the ability to make direct comparisons between these groups. Therefore, a longitudinal study design following the same cohort from youth to middle age is essential to gain in-depth insight into the long-term effects of childhood maltreatment on SDS and MDD and how these effects evolve over time.

Based on the observed age-specific patterns between childhood maltreatment and depressive outcomes, we offer the following suggestions for clinical and social practice. First, emotional neglect and emotional abuse should be prioritized in depression risk screening across all adult age groups, given their consistent and significant association with MDD. Second, early screening tools such as the CTQ could be incorporated into routine mental health assessments, especially for individuals with SDS, who might otherwise be overlooked in clinical settings. Third, clinicians and policymakers should adopt age-sensitive approaches that recognize generational differences in trauma reporting and emotional expression. Younger adults may benefit from proactive inquiries and open disclosure environments, whereas middle-aged adults may require more nuanced and culturally sensitive interventions. Public mental health strategies should address the covert nature of emotional maltreatment and promote trauma-informed care across age groups.

CONCLUSION

In conclusion, our study highlights the significant role of childhood maltreatment, particularly emotional abuse and neglect, as a key risk factor for SDS and MDD. These forms of maltreatment continue to have a long-term impact on mental health, with emotional abuse and neglect remaining significant predictors of depression even in middle-aged adults. This emphasizes the need for early screening and trauma-informed care to address childhood experiences of emotional abuse and neglect regardless of age.

ACKNOWLEDGEMENTS

The authors thank all of the participants in our study and sincerely acknowledge the technical support from the School of Public Health, Sun Yat-sen University.