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Youth exposure to environmental risk factors linked with aggression in adulthood

Early exposure to urbanicity, migration, abuse and cannabis or alcohol during youth strongly predicted violent aggression in adulthood, data published in Molecular Psychiatry suggest.

“Adverse experiences in adulthood, like exposure to violence, traumatic brain injury, or substance intoxication, can act as single triggers to increase the short-term risk of violence in mentally ill individuals as much as in control subjects,” Marina Mitjans, PhD, of Max Planck Institute for Experimental Medicine, Göttingen, Germany, and colleagues wrote. “However, comprehensive studies, including large numbers of individuals and replication cohorts, on pre-adult accumulation of environmental risk factors and their long-term consequences on human behavior do not exist.”

In a previous study, Mitjans and colleagues reported that accumulated environmental risk decreased age at schizophrenia onset. To determine whether accumulation of these risk factors during childhood would lead to violent aggression and criminal conduct independent of mental illness, the investigators examined this association in six independent cohorts. Urbanicity, migration, physical and sexual abuse were primary pre-adulthood risk exposures, and cannabis or alcohol were secondary risk factors.

Participants included four schizophrenia samples taken from the Göttingen Research Association for Schizophrenia data collection and two general population samples. Using data from questionnaires, interviews and charts, researchers applied the violent aggression severity score to those in the schizophrenia sample. They used history of forensic hospitalization or conviction for battery, sexual assault, manslaughter and/or murder as violent aggression proxy. In the general population sample, the investigators used the Levenson Self-Report Psychopathy Scale and the Zuckerman–Kuhlman Personality Questionnaire as proxies of violent aggression.

Each individual primary risk exposure — urbanicity, migration, physical and sexual abuse — and secondary risk exposure — cannabis/alcohol use — was marginally associated with higher violent aggression in adulthood. With the addition of any risk factor, this risk increased step wise, reflected by a stair pattern throughout all populations, according to a press release. Moreover, it was the accumulation of all these environmental risk factors (three or more) that strongly predicted violent aggression (OR = 10.5).

After conducting epigenome-wide association analyses to detect differential methylation of blood-derived DNA in some extreme group individuals (n = 142), the researchers found higher levels of histone-deacetylase1 mRNA in men with high-risk profile, indicating long-term epigenetic alterations that can be influenced by environmental factors, per the press release.

“This study should motivate sociopolitical actions, aiming at identifying individuals at risk and improving precautionary measures. Effective violence prevention strategies start early and include family-focused and school-based programs,” Mitjans and colleagues wrote. “Additional risk factors, interchangeable in their long-term consequences, like urbanicity, migration and substance abuse, should be increasingly considered. Health care providers are essential for all of these prevention concepts. More research on protective factors and resilience should be launched.” – by Savannah Demko

Disclosures: The authors report no relevant financial disclosures.