Mental Illness and Violence

The deliberate crash of a Germanwings commercial airline flight by a co-pilot, known to be suffering from depression, killing himself and all 149 others on board has yet again raised concerns about the relationship between mental illness and homicidal behavior. The perpetrators in several high profile mass murders in the United States in the past four years all suffered from severe mental illnesses. The news organizations that report on these events tend to regard mental illness as a single disease category and rarely dwell on the characteristics of the large number of distinctly different mental syndromes (diseases) that this descriptor can cover. Therefore, it is not surprising that the general public has a similarly vague conception of mental illness and is often unaware that each particular mental disorder (depression, schizophrenia, obsessive-compulsive disorder, anxiety etc.) is defined by a unique set of behaviors and thoughts that enable us to predict how those afflicted with the condition will act. 

When we consider the potential contribution of mental illness to acts of violence, it is essential that this be done in the context of the specific mental disorder thought to be involved. In the case of the Germanwings tragedy, we know that the co-pilot had a history of depression and was under the care of a psychiatrist at the time of the crash. If the depression suffered by the pilot motivated his decision to crash the plane, this association will have major implications for how we insure the safety and welfare of individuals not just in the airline industry but throughout society.  However, it is not at all clear how governments and regulatory agencies could devise a set of rules, based on the premise that an individual with depression may be a danger to others, that would reduce the probability of similar events occurring in the future. At any point in time, approximately 5% of the US population suffers from depression (Centers for Disease Control). Therefore, it would be impossible (and unjust) to implement legislation that would prevent those being treated for depression being in a position in which they have responsibility for the lives of others. 

When one examines the evidence of a link between mental illness and homicide, the facts are more complex than suggested by a cursory analysis of the Germanwings crash.  Among the many distinct mental disorders, only schizophrenia and substance abuse/addiction are consistently related to a higher risk of homicide of individuals unrelated to the perpetrator.  In depression, there is a higher risk of homicide-suicide in which the victims of the homicide are usually either family members (spouse or children) or friends but not of an increased risk of homicide per se.  Whichever mental illness contributed to the crash in the French Alps, it is certain that it affected the co-pilots perception of reality and ability to think rationally.  The key to preventing similar tragedies in the future may be to identify mental states (e.g. irrational, delusional, or paranoid), common to many mental diseases, that predispose to acts of violence, and to insure that persons with such symptoms receive effective and timely treatment; doing so, while respecting patient privacy and avoiding further stigmatization of those with mental disease, will not be a trivial task.