Several clinical and community studies have helped to establish a link between childhood maltreatment and adult psychopathology.(1-4) The association between child sexual and physical abuse with adult psychopathology, including higher rates of depression, substance abuse, anxiety disorders such as PTSD and and suicidal behaviors, have been substantiated in community studies involving samples of women.(5-9)

This association has not been as well researched in men. A subset of studies of men and women has found that a history of childhood sexual and physical abuse increases the likelihood of psychopathology,(5,10-12) but some studies suggest this relationship is seen to a greater extent in women compared to men for many of the psychiatric disorders.(5,13)

Even fewer studies have addressed psychiatric impairment related to neglect, emotional abuse and witnessing intimate partner violence. One community-based study of adolescents and young adults found that childhood neglect(14) and childhood emotional abuse(15) were associated with an increased risk of developing personality disorders. A community-based study(12) found emotional abuse was associated with adult mental health problems in both men and women.

While little attention has been given specifically to long-term effects of exposure to intimate partner violence, there is consensus that children and adolescents exposed to domestic violence are at increased risk for varied emotional and behavioral problems(16-17), including internalizing and externalizing problems.(18-21)

Cross-sectional community studies of adults reporting on their childhood history of maltreatment have been criticized for their reliance on retrospective self-reports, reporting biases and their inability to examine possible causal relationships.(22) However, studies in which exposure to maltreatment is measured prospectively typically involve samples that have come to the attention of child protection authorities or the courts—in other words, they are not community-based.

For example, Widom and colleagues(23-25) continue to follow abused and/or neglected children and matched non-victimized children from childhood into adulthood. They have found an increased risk for illicit drug use and substance abuse-related problems among maltreated children compared with controls.(23) The authors have found the pathways between childhood abuse/neglect and violent criminal behavior are different for men and women. For men, childhood maltreatment had both a direct effect on aggressive behaviour and an indirect one, through alcohol. For women, only the indirect path was found.(24)

In a very recent report, individuals experiencing childhood physical abuse and multiple abuse types were shown to be at increased risk of lifetime major depressive disorder, whereas those with a history of neglect were at increased risk for current major depressive disorder.(25) Sexual abuse was not significantly associated with elevated risk of depression; however, these individuals reported more depressive symptoms compared to controls(25) and were at increased risk for PTSD.(26)

Taken together, both longitudinal and cross-sectional studies establish that child abuse and neglect are associated with an increased likelihood of psychopathology in adolescence and adulthood.(22,27) They also indicate the importance of two broader issues.

First, is the issue of multifinality—the notion that similar exposures (childhood maltreatment subtypes) may be associated with different outcomes.

Secondly, not all individuals exposed to childhood maltreatment experience later psychopathology. Emerging research suggests that it is a combination of genetic and environmental factors (G x E), that serve as risk or protective factors for later psychopathology.

G x E: Risk and protective factors
Researchers have examined how genetic factors interact with exposure to maltreatment.(28,29) These studies investigated differences at a functional polymorphism in the promoter of the monoamine oxidase A (MAOA) gene.

Several studies have shown that individuals with a history of maltreatment and with the gene encoding for low MAOA activity have an increased likelihood of developing conduct disorder and antisocial personality disorder in both childhood and adulthood compared to individuals with a history of maltreatment and the gene for high MAOA activity.(28-31)

Some of these studies have been criticized for their exclusive focus on Caucasian males. A recent study examining the same G x E relationship in a more ethnically diverse population, involving both males and females, found that the protective high MAOA activity in the maltreated population is only found in Caucasians.(32)

Other studies have focused on another gene—a functional polymorphism in the promoter region of the serotonin transporter (5-HTT).

These studies have shown that individuals with one or two copies of the short (s) allele of the 5-HTT promoter polymorphism exhibit more depressive symptoms than individuals homozygous for the long (l) allele in adults with a history of child maltreatment or recent stressful events(33-34) and in maltreated children.(35)

Importantly, the study also showed that quality and availability of social supports were environmental factors that promoted resilience in maltreated children, even in the presence of the short allele.(35)

In two recent investigations, both 5-HTT and MAOA have been implicated in early alcohol use.(36-37) Maltreatment, 5-HTT and a G x E interaction predicted early alcohol use; increased risk was associated with the short allele.(36) Similarly, the short variant of the MAOA gene, associated with low MAOA activity, in combination with childhood maltreatment was implicated in higher rates of adolescent problem drinking in a population of 16- to 19-year-old males.(37)

Although further replication studies are necessary, the evidence to date suggests that important G x E interactions exist. This may explain why certain individuals exposed to childhood maltreatment develop adulthood psychopathologies, whereas other individuals do not.

Furthermore, exposure to childhood abuse and neglect constitutes a non-specific risk for many disorders (multifinality). Interactions between genes and the environment may offer clues regarding the pathways of multifinality.

Evidence-based interventions needed
It is clear that interventions to prevent maltreatment are needed, yet evidence-based interventions are scarce.(38) However, there is some good news on the horizon.

A home visitation program, the Nurse Family Partnership (NFP), has been shown effective in preventing child abuse and neglect and associated outcomes such as injuries. The NFP targets first-time, socially disadvantaged mothers. Visits begin prenatally and extend until the child is two years of age.(39) NFP nurses focus on the following goals: 1) promoting healthy prenatal behaviors; 2) improving child health and development by assisting parents in the competent care of their children; and 3) enhancing parents’ life-course development by encouraging parents’ education, work and pregnancy planning.

The NFP has been evaluated in three RCTs and is now being implemented across the US.(39) Of particular interest for psychiatrists, the 15-year follow-up of the earliest NFP trial conducted in Elmira, showed that youth whose mothers were in the nurse-visited group had fewer conduct disorder symptoms compared with the control group youth.

Although the NFP will not be the only approach for preventing child maltreatment, it is an effective targeted intervention for first-time, socially disadvantaged mothers and their infants. Hopefully, knowledge arising from the G x E interaction investigations will assist in determining approaches to prevention of impairment among maltreated children and thereby lower their risk for subsequent psychopathology.

References and suggested readings

_{1. Brown GR & Anderson B. Psychiatric morbidity in adult inpatients with childhood histories of sexual and physical abuse. Am J Psychiatry 1991; 148: 55-61.}

2. McCauley J, Kern DE, Kolodner K, Dill L, Schroeder AF, DeChant HK, et al. Clinical characteristics of women with a history of childhood abuse: unhealed wounds. JAMA 1997; 277: 1362-1368.

3. Weiss EL, Longhurst JG & Mazure CM. Childhood sexual abuse as a risk factor for depression in women: psychosocial and neurobiological correlates. Am J Psychiatry 1999; 57: 816-823.

4. Kendler KS, Bulik CM, Silberg J, Hettema JM, Myers J & Prescott CA. Childhood sexual abuse and adult psychiatric and substance use disorders in women: an epidemiological and cotwin control analysis. Arch Gen Psychiatry 2000; 57: 953-959.

5. MacMillan HL, Fleming JE, Streiner DL, Lin E, Boyle MH, Jamieson E, et al. Childhood abuse and lifetime psychopathology in a community sample. Am J Psychiatry 2001; 158; 1878-1883.

6. Jumper SA. A meta-analysis of the relationship of child sexual abuse to adult psychological adjustment. Child Abuse and Neglect 1995; 19: 715-728.

7. Duncan RD, Saunders BE, Kilpatrick DG, Hanson RF & Resnick HS. Childhood physical assault as a risk factor for PTSD, depression, and substance abuse: findings from a national survey. Am J Orthopsychiatry 1996; 66: 437-448.

8. Mullen PE, Martin JL, Anderson JC, Romans SE & Herbison GP. The long-term impact of the physical, emotional, and sexual abuse of children: a community study. Child Abuse Negl 1996; 20: 7-21.

9. Lipman EL, MacMillan HL & Boyle MH. Childhood abuse and psychiatric disorders among single and married mothers. Am J Psychiatry 2001; 158: 73-77.

10. Fergusson DM, Horwood LJ & Lynskey MT. Childhood sexual abuse and psychiatric disorder in young adulthood, II: psychiatric outcomes of childhood sexual abuse. J Amer Acad Child Adolesc Psychiatry 1996; 35: 1365-1374.

11. Kessler RC, Davis CG & Kendler KS. Childhood adversity and adult psychiatric disorder in the US National Comorbidity Survey. Psychol Med 1997; 27: 1101-1119.

12. Edwards VJ, Holden GW, Felitti VJ & Anda RF. Relationship between multiple forms of childhood maltreatment and adult mental health in community respondents: Results for the adverse childhood experiences study. Am J Psychiatry 2003; 160: 1453-1460.

13. Horwitz AV, Widom CS, McLaughlin J & White HR. The impact of childhood abuse and neglect on adult mental health: a prospective study. J Health Soc Behavior 2001; 42(2): 184-201.

14. Johnson JG, Smailes EM, Cohen P et al. Associations between four types of childhood neglect and personality disorder symptoms during adolescence and early adulthood: findings of a community-based longitudinal study. J Personal Disord 2000; 14: 171-187.

15. Johnson JG, Cohen P, Smailes EM et al. Childhood verbal abuse and risk for personality disorders during adolescence and early adulthood. Compr Psychiatry 2001; 42: 16-23.

16. Fantuzzo, JW & Mohr WK. Prevalence and effects of child exposure to domestic violence Future Child 1999; 9: 21-32.

17. McCloskey LA, Figueredo AJ & Koss MP. The effects of systemic family violence on children’s mental health. Child Dev 1995; 66(5): 1239-61.

18. Yates TM, Dodds MF, Sroufe A & Egeland B. Exposure to partner violence and child behavior problems: A prospective study controlling for child physical abuse and neglect, child cognitive ability, socioeconomic status, and life stress. Dev Psychopathol 2003; 15: 199-218.

19. Hazen AL, Connelly CD, Kelleher KJ, Barth BP & Landsverk JA. Female caregivers’ experiences with intimate partner violence and behavior problems in children investigated as victims of maltreatment. Pediatrics 2006; 117(1): 99-109.

20. McFarlane JM, Groff JY, O’Brien JA & Watson K. Behaviors of children who are exposed and not exposed to intimate partner violence: an analysis of 330 black, white and Hispanic children. Pediatrics, 2003; 112 (3 Pt 1): e202-207.

21. Wolfe DA, Crooks CV, Lee V, McIntyre-Smith A & Jaffe, PG. The effects of children’s exposure to domestic violence: A meta-analysis and critique. Clin Child Fam Psych Rev 2003; 6(3): 171-187.

22. Widom CS, Raphael KG & DuMont KA. The case for prospective longitudinal studies in child maltreatment research: commentary on Dube, Williamson, Thompson, Felitti, and Anda (2004). Child Abuse Negl 2004; 28: 715-722.

by Andrea Gonzalez, MA (PhD candidate, University of Toronto) and
Harriet L. MacMillan, MD, FRCPC, Professor of Psychiatry and Behavioural Neurosciences and Pediatrics, McMaster University