Are siblings more at risk for developing dual diagnosis?


U.S. children are more likely to grow up in a household with a sibling than with a father, according to a study shared by the National Institutes of Health. It also explains, “Unlike friendships, sibling relationships are nonelective, they usually imply a life-long bond, and the sibling role structure encompasses both egalitarian and complementary elements.”

Several research studies highlight sibling-led enculturation, specifically, brothers or sisters of one with mental health disorders and addiction are likely to have mental distress of his or her own, and may also attempt self-medication.

The trickle-down effects

The National Institutes of Health offer data from several studies on mental and behavioral issues and siblings.

  • About half students in the eighth to 10th grade who admitted smoking in a given month got the cigarettes from a sibling
  • Bad relationships with a brother or sister before age 20, along with a family history of depression, predicted both the manifestation of major depression and the regularity of use of mood-altering drugs by age 50
  • Behavioral problems were linked to a sibling’s depression; National Center on Addiction and Substance Abuse at Columbia University illustrates tandem correlations between both sibling’s levels of substance abuse
  • Parent differential treatment – giving one child more focus – preceded mental distress in other children and instigated substance abuse. Parents surveyed said differential treatment was often a response to one of their children being addicted to substances

Brother to brother influence

“For brothers,” bad influence may be strongest compared to other sibling pairs, according to an NIH study on siblings and delinquency. “The conditional effects of older sibling delinquency and relationship quality were shown to predict change in younger sibling delinquency through adolescence,” the study notes.

Developmental outcomes of the more impressionable sibling – be they for good or for ill – depend on what the more influential sibling’s behavior, epigenetic traits and whether conditional effects are for mentorship or deviancy training.

Research professor Mark Feinburg, Ph.D., has studied sibling relationships extensively. Antisocial behavior can be a symptom of manifested mental disorder and/or substance abuse. In one of his studies, he parses negative sibling cues spurring antisocial behavior into at least two models:

  1. “Coercive processes model is that negativity and coercion in the sibling relationship represent a ‘training ground’ for the development of a generalized negative, conflictual, and coercive interpersonal style. Youth adopt coercive behavior patterns as they learn through social reinforcement that such behavior is a successful means of obtaining a goal. This coercive interpersonal style is associated with poor self-control, including decreased ability to tolerate frustration, manage negative emotions, and communicate calmly,” Feinburg and fellow study authors explain.
  2. Deviancy training. “Siblings aid in deviancy training by serving as antisocial models, reinforcing antisocial behaviors and attitudes, and colluding to undermine parental authority. Siblings also act as partners in crime, such as when they become involved together in risky behaviors such as delinquent or criminal acts or substance use.”


If a teen is being pulled into the throes of co-occurring mental disorder and substance abuse by a sibling, there are practical methods to lift him out.

“Research has clearly established that the transition to adolescence is characterized by increasing assertion of independence and autonomy, in part reflected by increases in nonparental social influences,” according to Wichita State University Professor Sabina Low. Her study finds siblings’ direct or indirect methods of modeling and mentoring can have instrumental outcomes.

Feinberg and colleagues conclude clinicians need to be mindful of sibling influences, investigate the nature of sibling relationships and perceived fairness of parenting from all family members. Clinicians can take an extra step to include the outside sibling into the holistic healing process.

For the sibling who’s struggling against developing disorders and addictions, there is a wealth of applicable information and tools with the sibling support facet of the Self Help Addiction Resource Centre.

White River Academy is a therapeutic boarding school for boys 12-17 who are dealing with addiction and mental health issues. Call our 24/7 helpline for enrollment details.

About the author

Kristin Currin-Sheehan is a mindful spirit swimming in metaphysical pools with faith as her compass. Her cover: a 30s-something Cinderella breadwinner of an all-sport blended family. Her repertoire includes writing poetry, lifestyle articles and TV news; editing, radio production and on-camera reporting. 

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