The presence of a wide array of psychiatric illnesses in parents significantly increases the likelihood that their offspring will attempt suicide and engage in violent, offending behaviors after the age of 15 years, a population-based Danish cohort study indicates.
"Children of parents with a history of psychiatric disease and substance use may be at heightened risk of additionally experiencing other adversities, such as maladaptive parenting styles, abuse, neglect, and financial hardship," lead author Pearl Mok, PhD, University of Manchester, United Kingdom, told Medscape Medical News in an email.
"Shared genetic vulnerability to psychiatric disorders and impulsive-aggressive traits may also contribute partly to the links," she added.
"So interventions that improve parenting skills and parental relationships as well as family therapy may be useful."
The findings were published online August 31 in JAMA Psychiatry.
The study included everyone born in Denmark to Danish parents from 1967 to 1997. Participants also had to be living in the country when they were 15 years of age. Overall, the cohort included 1,743,525 individuals, approximately half of whom were female.
Participants were followed from their 15th birthday to the occurrence of an adverse outcome or through 2012, whichever came first.
A total of 44,472 cohort members (2.6% of the study population) made an initial attempt at suicide, and 55,404 (3.2%) were convicted of a first violent offense during the study period. The median age was 21.6 years for the first suicide attempt and 20.6 for conviction of the first violent offense.
Violent offenses included conviction for homicide, assault, robbery, aggravated burglary, arson, possessing a weapon in a public place, violent threats, extortion, human trafficking, abduction, kidnapping, rioting or other public-order offenses, terrorism, and all sexual offenses with the exception of possession of child pornographic material.
Higher Rates Across All Psychiatric Disease
"Histories of mental illness for cohort members' parents were obtained from the Psychiatric Central Research Register," Dr Mok noted.
The team found that the risk for offspring suicide attempt and violent offending were elevated across the full spectrum of parental psychiatric disease.
The association between parental psychiatric disease and both suicide attempt and violent, offending behavior was also "particularly strong" when a parent or parents had been diagnosed with antisocial personality disorder, extreme cannabis misuse, and parental attempt at suicide themselves, the investigators report.
Incidence rate ratios were the most elevated for parental diagnoses of antisocial personality disorder (suicide attempt, 3.96; violent offending, 3.62) and cannabis misuse (suicide attempt, 3.57; violent offending, 4.05) and for parental suicide attempt (suicide attempt, 3.42; violent offending, 3.31).
Parental mood disorders and, in particular, bipolar disorder conferred more modest increases in risk, the researchers note.
"Risks for offspring suicide attempt and violent offending were elevated across the full spectrum of parental psychiatric disease, except for Alzheimer disease, for which no significant link with offspring violent offending was found," the researchers note.
Both Parents Affected
A predisposition to violent, offending behavior was twice as likely to be present among offspring for whom both parents had been diagnosed with a psychiatric illness in comparison with those for whom only one parent had been so diagnosed.
"The associations between parental psychiatric disease and offspring violent offending were stronger for female than for male offspring (P < .001)," the investigators add. Again, this was especially the case when both parents had a history of psychiatric illness.
The investigators note that the links between parental psychiatric disease and offspring suicide attempts and violent behaviors remained significant after adjusting for potentially confounding socioeconomic factors.
As Dr Mok explained to Medscape Medical News, substance misuse and antisocial personality disorder, as well as suicidal behavior and perpetration of violence, are often characterized by behavioral dysregulation and impulse-aggressive traits.
"Some other studies have suggested that these traits are heritable," she observed, "and the intergenerational transmission of such traits may thus contribute to the particularly elevated risk for suicidal behavior and violent offending among those with a parental history of antisocial personality disorder, substance misuse, and attempted suicide."
Dr Mok also emphasized the fact that in their study, all cases of parental mental disorders were severe enough to have resulted in secondary care treatment.
The researchers are not suggesting that parental cannabis use per se confers an elevated risk for offspring to attempt suicide and perpetuate violence: "Our measure only delineates the most extreme end of the cannabis misuse spectrum," she said.
"And acute intoxication, dependence and withdrawal syndromes, or psychotic disorders could be some of the reasons for secondary care admissions due to cannabis misuse."
The authors recommend that any physician who treats adults with mental illness should evaluate the psychosocial needs of their children and should intervene in a way that might ameliorate the effects of parental substance misuse so as to reduce the risk for suicide and violence in their children.
Much to Commend
In an accompanying editorial, David Brent, MD, and Nadine Melhem PhD, both from the University of Pittsburg School of Medicine, in Pennsylvania, along with Holly Wilcox, PhD, Johns Hopkins University School of Medicine, Baltimore, Maryland, write that there is "much to commend" in the current study, including the range of psychiatric disorders analyzed among the parents and the sample size.
On the other hand, "the impact of parental psychiatric disorder on suicide attempt and violent offending may still be overestimated, as there are likely to be other shared environmental factors correlated with parental disorder that could contribute to suicidal behavior and violent offending, such as maltreatment, separation from parents, and intrauterine drug and alcohol exposure," they observe.
Indeed, intrauterine exposure to harmful substances might help explain why cannabis misuse was so strongly implicated in the risk for violent behavior, the editorialists suggest.
They also note that psychiatric disorders in the offspring were not known, or at least not reported, and that mental illness among the offspring is likely to be a "major final common pathway connecting parental disorders with offspring suicidal behavior and violence," they write.
Nevertheless, the editorialists felt that the study had singled out an important finding, namely, that when patients with a history of substance abuse, antisocial disorder, or suicide attempt are under medical care, practitioners need to assess their children as well.
To make sure this happens, physicians need to recognize the fact that psychiatric disorders tend to run in families. In addition, the editorialists state that assessment of any offspring of affected parents should be a "reimbursable clinical activity."
"We do not need any more elegant studies to make a case for investment in the prevention of mental disorders, violence, and suicidal behavior," they conclude.
"What we do need is the scientific and political will to align clinical infrastructure and reimbursement strategies with the extant scientific evidence [and] put to use what we know now about how to prevent 'common sources of family unhappiness' and thus prevent suicide and violence in the future," they conclude.
The study was supported by a grant from the European Research Council. Dr Mok has disclosed no relevant financial relationships. Dr Brent has received royalties from Guilford Press and from the electronic self-rated version of the Columbia Suicide Severity Rating Scale from ERT, Inc. He also serves as an UptoDate psychiatric section editor has received consulting fees from Healthwise.
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Cite this: Psychiatric Illness in Parents, Suicide/Violence in Kids - Medscape - Aug 31, 2016.