A within individual designed epidemiological study that linked individual SSRI prescriptions in the Swedish Prescribed Drug Register with individual violent crime convictions in the Swedish national crime register committed between January 1, 2006 and December 31, 2009 (n = 8,377) found that SSRI treatment for adolescents and young adults between 15 and 24 years of age was associated with a 45% increased risk of being convicted of a violent crime with low SSRI exposure being associated with a 62% increased risk of being convicted of a violent crime.

While this epidemiological study cannot causally link SSRIs to violent crime much less mass shootings there are three decades of consistent and substantial evidence, including from the clinical trials for SSRIs themselves, that they can increase the risk of violent behavior which would include mass shootings in which most perps are later revealed to have been medicated with SSRIs or other antidepressants.

A systematic review of 13 double blind placebo controlled RCTs of SSRIs and SNRIs given to healthy adult volunteers found that they doubled their risk of suicidality and violence with 1 out of 16 volunteers being harmed by the medication.

A review of the clinical trial data for the antidepressants Paroxetine (GSK), Sertraline (Pfizer) and fluoxetine (Eli Lilly) reveals that participants in the treatment groups experienced much higher rates of “hostile events”, including homicidal ideation, that led to discontinuation in the trial than placebo group participants without necessarily being statistically significant in the smaller healthy volunteer trials. These hostile events occurred during both therapy and withdrawal for both adult and pediatric patients, especially pediatric patients with OCD who were found to have a 17x higher risk of hostile events when treated with paroxetine (Paxil).

Another review of the medical literature on SSRIs notes that they can have stimulant-like side effects including paranoia, mania, psychosis and hostile behavior. Much of this was revealed by Internal documents from Eli Lilly obtained through discovery in a product liability lawsuit. Numerous case reports identify treated individuals feeling an alien or ego-dystonic quality and behavior completely out of character for the treated individual including adolescent fluoxetine (Prozac) patients developing symptoms of nervousness, anxiety, agitation, and insomnia at twice the rate of patients in the placebo arm of the trial. One case report of a 12 year old fluoxetine (Prozac) patient participating in the same clinical trial notes that he had vivid dreams about becoming a school shooter and killing his classmates, his parents and himself 38 days after beginning the study. He eventually became suicidal and was hospitalized for 17 days.

A case series study of psychiatric inpatient admissions to Yale-New Haven Hospital over a 14 month period between January 1997 and February 1998 (n = 533) determined that 43 of them (8%) were cases of mania or psychosis related to antidepressant prescriptions. 70% of those admitted for antidepressant related mania or psychosis had been prescribed SSRIs with Paroxetine (Paxil) and Sertraline (Zoloft) making the majority of SSRI cases. Many of the SSRI inpatients experienced paranoid delusions or auditory hallucinations that encouraged them to commit suicide, particular those who were prescribed fluoxetine (Prozac).

A review in The International Journal of Psychiatric Research explains that SSRIs can cause serotonin syndrome that can lead to symptoms like those described above in severe cases and cause mania in individuals with undiagnosed bipolar disorder.