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Nick Reiner was charged Dec. 16 with killing the 78-year-old actor and director Rob Reiner and his wife, Michele in their Los Angeles home.

"Their son Nick had been in rehab many times,” wrote Bill Linnel in a Facebook post. “I used to work in a rehab, as a Certified Residential Medication Aide,  passing out medications. Addicts are typically given SSRI antidepressants. This explains the son's freakish violence,” 

Across the country, in Massachusetts, hundreds mourned Ella Cook, 19 and freshman MukhammadAziz Umurzokov, 18, who were killed on Dec. 13 when a former Brown grad student, 48-year- old gunman entered a study session in a Brown academic building and opened fire on students. Nine other students of Brown were wounded.

“What's causing this unprecedented madness?” Linnel  wrote, “ mass distribution of SSRI antidepressants cause freakish, maniacal violence and suicide. They should have been banned.”

At the American Community Media national briefing on Mass Shootings and Gun Violence, Dr. Ragy Girgis, professor of clinical psychiatry at Columbia University who has studied the relationship between mental illness and mass shootings said,“ Nothing is less of a contributor to mass shootings than antidepressant medications and psychiatric medications in general. I mean, we published this, the data is out there,” said the doctor who began to study violence and schizophrenia about 10 years ago. 

Is there a relationship between mental illness and mass shootings

Dr. Girgis assembled the largest database of mass murder in existence.  “What we found was that the vast majority of mass shootings in particular, are not related to mental illness at all,” said Dr Girgis.

Mass shootings when caused by mental illness typically involves severe psychotic disorders marked by delusions or hallucinations that compel violence. In such cases, individuals may believe their lives are in danger or hear voices instructing them to kill. These circumstances are uncommon and account for only about 5 percent of mass shootings in the United States.

95% of mass shootings are not related to mental illness. 

Killer’s distinct psychological profile 

Dr. Girgis and his team found that public mass shootings share a distinct psychological profile with three core features. First, perpetrators often exhibit a strong fascination with or affinity for firearms, making gun availability a critical factor. Second is nihilism, a profound sense of emptiness and meaninglessness that, in its most severe form, is closely linked to suicidal thinking. Third is a form of narcissism understood in psychodynamic terms, rooted not in grandiosity but in deep low self-esteem that is externalized through violence against others.

The role of suicide as a trigger for mass killing with a firearm

About half of mass shooters die by suicide during the attack, a fact that helps explain both their choice of weapon and the dynamics that lead to these crimes. Research shows that firearms are most often chosen not only for their lethality toward others, but because they are the method the perpetrator intends to use to take their own life.  Primary barriers that typically prevent mass violence are personal moral beliefs, social values shaped by family and community, and fear of arrest and incarceration. When an individual has already decided to die, that final barrier is effectively removed, and because many attackers plan both the shooting and their suicide weeks, months, or even years in advance, the path to carrying out a mass shooting becomes far easier.

So what causes mass shootings? 

Recent research has closely examined the role of firearms and gun policy in mass shootings, and the findings are consistent with the broader gun violence literature. Weaker state firearm laws are strongly associated with higher rates of mass shootings and more victims per capita, and similar patterns emerge when examining federal policies such as the former Assault Weapons Ban. Most firearms used in mass shootings are legally acquired, underscoring that guns typically enter circulation lawfully before being misused. Taken together, the evidence points to the need not only for stronger firearm policies but for consistent and effective enforcement of existing laws.

“Strengthen our firearm policies, and really, we need to enforce the laws. Some firearm laws, especially in certain states are just simply not enforced,” said Dr Gerges. 

Homicides in the United States have been on a steep downward trajectory

Data from Jeff Asher's Real-Time Crime Index (RTCI) and other sources confirm significant drops in U.S. homicides, with analyses showing steep declines in 2023 and accelerating into 2024-2025, exceeding 40% drops in some periods or locations from pandemic highs, representing a historic fall back to pre-pandemic or lower levels, even as debates continue on the exact causes. 

Jeff Asher’s Real-Time Crime Index (RTCI) is a near-real-time crime tracking tool designed to show how crime trends in the U.S. are evolving month-to-month, rather than waiting many months (or years) for official national statistics like the FBI’s Uniform Crime Report to be released.  

“While the pace of change varies by city and state, the overall trend is clear: nearly every part of the United States has seen substantial declines in homicide in recent years. Looking at 12-month rolling averages, homicides in Detroit have fallen by roughly 76 percent from their peak in 2021–2022, according to Dr. Webster. 

Other cities with historically high homicide rates show similar progress. Baltimore, Philadelphia, and New Orleans have each experienced declines of about 60 percent over the same period. Importantly, the rate of decline appears to be accelerating, leading Dr. Webster to predict that once all data for the year are finalized, the nation could record its lowest murder rate since the FBI began publishing national crime statistics in 1960. 

Notably, the most recent and sharpest drops have occurred among young adults in their twenties.

What's caused these historic reductions in gun violence

The spike in violence from 2019 to 2020 marked the largest single-year increase in firearm homicides in U.S. history. It coincided with the onset of COVID-19 shutdowns and, in many cities, with large-scale protests against police violence. Some of the sharpest increases in gun violence occurred in cities that experienced the most destructive unrest, where violence involved both protesters and police and where trust in law enforcement and government was already fragile.

At the same time, the country saw historic surges in firearm purchases, while nearly every public system, policing, courts, prisons, social services, schools, and health care, was strained and weakened by the pandemic, limiting their ability to respond effectively to rising instability.

“As the pandemic has receded, those systems have gradually regained capacity, helping drive the recent decline in violence. Federal funding under the Biden administration injected significant resources into cities during the COVID crisis, much of it directed toward violence reduction,” said Dr Webster. 

The bipartisan Safer Communities Act expanded background check requirements but, just as importantly, functioned as a major funding vehicle for community violence intervention programs, law enforcement support, mental health services, and the implementation of extreme risk protection order laws. Many cities also created or expanded dedicated offices of violence prevention and scaled up “group violence reduction” strategies that combine focused law enforcement with social services and community-based support for individuals at highest risk of involvement in gun violence.

Ghost gun kits bypassed the regulatory system 

A month after the legislation was passed in 2022, the Biden administration adopted a new rule regulating ghost gun kits, or privately made firearms, which had previously bypassed the regulatory system and could not be traced because they were exempt from background checks and standard recordkeeping.

Dr. Daniel Webster, who closely studied these weapons in Baltimore, found that ghost guns were disproportionately ending up in the hands of underage youth and individuals with violent criminal histories who were legally prohibited from purchasing firearms. After an exponential rise in ghost gun recoveries between 2017 and 2022 in Baltimore, California cities, and elsewhere, those numbers have since “dropped off a cliff,” with the weapons now far less likely to be linked to acts of violence.

Dr. Webster also cautions that gun violence follows longer-term cycles shaped not only by specific policies and programs but by broader cultural shifts. Among those shifts, he notes, are declining alcohol consumption, particularly binge drinking, a strong risk factor for gun violence, and possible changes in attitudes among young people. In conversations with youth in Baltimore, he has sensed that after years of exposure to violence, some may be reaching a point of fatigue, prompting behaviors that could also be contributing to the recent decline.

Gun violence functions like a social contagion: when shootings rise, one incident can trigger another, creating cascading harm

While the recent declines in gun violence represent a meaningful victory, Dr. Daniel Webster cautions that progress remains fragile. From a public health perspective, he explains, gun violence functions much like a social contagion: when shootings rise, one incident can trigger another, creating cascading harm. But the dynamic also works in reverse.

Every effective policy, program, or intervention that prevents a shooting today can avert additional shootings in the future that might otherwise have followed. That momentum has helped place the country on a promising downward trajectory, Webster said, though he expressed concern about whether those gains can be sustained if federal attention and resources shift elsewhere.

“ I would really underscore is that these are preventable  It's easy for people to just say, oh my god, it'll never stop. There's nothing we can do about it. Stronger gun laws do lead to fewer mass shootings. They don't eliminate it completely 

“This is preventable. I think that's the most important thing,” said Dr. Girgis

“If people who shouldn't have guns don't have guns, we can eliminate this,” said Sarah Lerner, co-founder of Teachers Unify To End Gun Violence