How Are Substance Abuse and Violence Related?

Can drug and alcohol use really cause people to become violent?

While television shows and movies featuring drunken bar brawls may seem exaggerated, the sheer volume of research looking at substance abuse and criminal behaviour suggests that substance abuse does play a role in many different forms of violence. Certainly, research exploring the link between alcohol, drugs, and aggression goes back for decades with hundreds of new studies coming out each year.

Even when looking at crime statistics alone, the link between substance abuse and violence is certainly clear enough. According to Bureau of Justice statistics, more than 750,000 crimes linked to alcohol or drug intoxication were committed in the United States alone in 2007. Along with the human cost involved, the economic cost cost of substance-related violence has been estimated at exceeding 120 billion dollars a year.

But this trend is hardly limited to the United States. One 2014 meta-analysis examining homicide rates across nine different countries found that 48 percent of homicide offenders had alcohol in their systems at the time of their offense while 37 percent were intoxicated. Though not every country provides crime statistics linked to substance use, those countries that do highlight how often drug and alcohol use is linked to violent crimes.

Still, despite the sheer volume of research studies demonstrating the connection between substance use and violence, the question of why such a connection exists is hard to answer. Not only do these different studies focus on fairly narrow populations (i.e., hospital inpatients, male prisoners, etc.), but they often varie widely in terms of the methodology used and the kind of questions being asked. For example, many of these studies focused on certain forms of violence, i.e., domestic abuse. As well, there have been thousands of different studies that have come out over the past decade alone which makes it extremely difficult for researchers to keep track of them all.

One way that researchers have been able to keep up with the sheer volume of new research coming out has been through the use of meta-analyses combining the results of multiple studies to look at underlying trends. Since 1985, numerous meta -analyses have come out examining the link between substance use and violence. Again though, these meta-analyses become increasingly narrow in their scope by focusing on specific populations or specific forms of violence. Though many of these meta-analyses have similar conclusions,coming up with a comprehensive overview that can make sense of the substance abuse-violence link has become harder than ever.

With this in mind, a new research study published in the journal Psychology of Violence presents the results of an ambitious new meta-analysis looking at the different meta-analyses that have come out in previous years (making it a meta-meta-analysis). For their research, Aaron Duke and a team of fellow researchers at the Yale University School of Medicine examined thousands of studies published between 1985 and 2014. They then identified 32 meta-analyses assessing the role of drugs and alcohol in violence and which also provided additional variables that could be studied further. These factors included gender, age range, type of substance used (alcohol, marijuana, illicit drugs, etc.), type of violence, and methodology. This allowed the researchers to conduct separate meta-analyses for these different factors to see how they influenced the substance abuse/violence link.

As expected, every meta-analysis showed a significant relationship between substance abuse and violence. Interestingly enough, the relationship between drug/alcohol use and violence appears to hold up across a wide range of different populations and types of violence, i.e., violence in the community, violent criminal recidivism, etc. Also, while drug and alcohol use are both linked to violence, the highest risk occurred when drugs and alcohol were used in combination.

One unexpected finding was that alcohol use was almost as strongly linked to victims of violence as it is to perpetrators of violence. In particular, abusing alcohol seems to be significantly linked to risk of being physically assaulted or injured though the link with drug use doesn't appear to be quite as strong. Also, the risk of violent acting out while under the influence of drugs or alcohol was significantly higher for men than women, something that remained consistent when all other demographic factors were taken into account.

The researchers also found that psychiatric diagnosis seems to play a role in substance-related violence with the risk being especially high in people diagnosed with psychotic disorders such as schizophrenia or schizoaffective disorder. This may be due to the high rate of substance abuse often found in psychiatric populations though, again, most people with a psychotic condition do not commit serious acts of violence.

Alcoholism Essential Reads

Why Findings on Alcohol and Health Are So Confusing

Alcohol Use Is Getting Deadlier in the United States

Though there are still limitations with using meta-analyses, they are a good way of combining results from thousands of studies to get a look at the "big picture." As Aaron Duke and his colleagues point out in discussing their findings, there does seem to be a strong link between the use of alcohol and/or illegal drugs and virtually every form of violence they looked at. Furthermore, this link applies to victims of violence as well as perpetrators.

While the link between alcohol and violence is already well-known, it is important for policymakers and the public to recognize that drugs and alcohol can also increase the risk of becoming a victim of violence. This research also highlights how important treatment for substance abuse can be in preventing future violence and making communities safer.