Antidepressants and Violence: A Link in Search of a Cause
What a new study on antidepressants and youth violence does and doesn’t say.
Posted Sep 30, 2015
Antidepressants such as fluoxetine (Prozac), sertraline (Zoloft) and Lexapro have carried major warnings for over a decade related to new or worsening suicidal behavior in children and young adults. A possible link, however, between this class of selective serotonin reuptake inhibitor (SSRI) antidepressants and other types of violent behavior has been more difficult to find, with different types of studies finding different results. To look more closely at this question, a recent study from Sweden was published that compared the same individual while the person was and was not taking an antidepressant.
Using large national registries, over 850,000 individuals were identified who were prescribed an SSRI medication. The authors then quantified the cumulative dose of SSRIs and divided subjects into groups of low, moderate, and high. From other registries, arrest and conviction records were examined and compared to the medication histories.
The main finding of the study, and the one that received the most press, was that for both males and females between the ages of 15 and 24 only, there was a statistically significant increase in the rate of violent crime during the period someone was taking the medication compared to the intervals when they weren’t. The “hazard ratio” for the 15-24 age group was 1.4 which roughly translates into a 40% increased likelihood. Described in the original study but not well reported by many press articles, however, was the important fact that this risk was increased only among those with low SSRI doses and not those with moderate or high overall SSRI exposure.
What does this all mean? As is often the case, the authors of the study themselves are rather cautious. While obviously concerned that it is possible that SSRIs may actually cause violent behavior in a small minority of people, they fully recognize that other explanations are possible. These include the possibility that what is driving the violent behavior is medication undertreatment, based on the finding that the risk with violence was only found among individuals who were likely taking subtherapeutic doses. As reported by MedScape, one of the study authors, Seena Fazel, states: "Our own view is that some evidence suggests that it's a bit more complicated than that, because we found a link with subtherapeutic doses of SSRIs, and that would suggest to us that it may be that it's actually a lack of treatment [and] it could be residual symptoms that are driving this link.” At the same time, if antidepressants really worked wonders for young people, we should see that therapeutic SSRI usage was associated with a reduced risk of violent behavior, which it wasn’t.
A couple other factors also deserve mention. The idea of comparing periods on and off medication within the same individual is a clever design, because many individual factors that might be related to risk of violence, like one’s socioeconomic status or DNA, are held constant. However, because the period of medication use was not randomized (and couldn’t be), it introduces the very likely complicating issue that individuals were taking medications during times when they were feeling more depressed, anxious, and angry to start with, and thus at higher risk of acting violently. Finally, it is important to note that a statistically significant association certainly does not mean that most people taking antidepressants are out there hurting others. When taking SSRI medications, the conviction rate of violent crimes was at a 1.0% rate compared to 0.6% without medications.
Like with most research, the study raises more questions than it answers. In my own practice, I have certainly observed young people become quite agitated when given SSRI antidepressants and have needed to stop the medication. This can be a tough call because it can be difficult to figure out whether the behaviors are due to the original problems getting worse (which might require more medications) or whether the medication itself is the problem. At the same time, I’ve also had many more patients tell me they feel less stressed and angry when taking SSRIs. Such is probably the reality with antidepressants. While this issue gets sorted out, we need to be able to exercise caution with SSRI medications, like any other, without over-reacting and writing off what can be an important tool in providing relief.
@copyright by David Rettew, MD
David Rettew is author of Child Temperament: New Thinking About the Boundary Between Traits and Illness and a child psychiatrist in the psychiatry and pediatrics departments at the University of Vermont College of Medicine.