Depp v Heard trial talks about drugs – but do they really make people violent?

The role of drugs in intimate partner violence is much more complex than one of cause and effect, writes Ian Hamilton

The data is overwhelming and depressing (AP)

It hasn’t taken long for drug use to be raised in the Depp v Heard trial. After all, celebrity and drug use is taken for granted sometimes; fame appearing to provide both the means and access to all manner of substances.

But the role of drugs in this trial is a much more sinister one. Amber Heard alleges Johnny Depp went on drug binges, disappearing for days at a time and returning “drunk, high and angry”.

Depp himself admits having used strong opiates like Roxicodone, alcohol and cocaine, but insists that he has a healthier relationship with these substances than he had in the past. This is contested by Amber Heard as she believes his use of drugs was instrumental in the violence she suffered during their relationship.

Not for the first time, drugs are used to explain violence and, in this case, it is suggested they act as a trigger for domestic violence. There is a strong association between intimate partner abuse and drugs including alcohol. The data is overwhelming and depressing: 40-60 per cent of cases of domestic violence involve drugs. An estimated 70 per cent of victims are more likely to drink alcohol excessively compared to peers who haven’t experience abuse.

So, whether you are a perpetrator or a victim, there is a greater chance that alcohol and other drugs are involved and that you will have a problem with these substances. But is there sufficient scientific evidence to move beyond association and say that drugs cause domestic violence?

This is strongly contested by some organisations that advocate for victims, who suggest that it is dangerous and misleading to blame or excuse the behaviour of (mainly male) perpetrators based on their consumption of alcohol and other drugs. They think this creates a false narrative of a man who is otherwise passive becoming aggressive based on his exposure to psychoactive drugs. In other words, remove the drugs and there would be less chance of violence.

This has a logic to it, as we know that many drugs do alter the way we think and behave – after all, that is why many of us use drugs like alcohol. We want to change how we feel and think, and in that sense these drugs do that very effectively. But are they capable of turning someone from a calm, rational being to one that can inflict violence on those closest to them?

The evidence suggests that while alcohol and other substances can cause arousal and disinhibition, this is not to the extent that an individual loses control and is unable to take responsibility for what they are doing. We know this because perpetrators of domestic violence stop inflicting physical or psychological damage when a third party steps in, such as the police or other members of the family.

Despite lawyers using intoxication and drug use as a mitigating factor when defending cases of domestic violence, the science does not support that position. Sustaining this myth creates injustice to victims and perpetrators alike.

To keep up to speed with all the latest opinions and comment sign up to our free weekly Voices Dispatches newsletter by clicking here

Victims are short-changed on justice as punishment is often diluted on the basis that perpetrators were not entirely responsible for their actions. Equally, those responsible for this type of violence may believe they have no control or responsibility for their actions – a damning scenario that limits their capacity to change behaviour.

The role of drugs in intimate partner violence is much more complex than one of cause and effect. Drugs are often used by (mainly) men to control their female partners, limiting access to drugs or demanding sex in exchange for drugs or using drugs to apologise for abusive behaviour. Likewise, victims may use substances to cope with various forms of abuse – drugs are often the only constant in their lives helping them survive horrific abuse.

Irrespective of how the Depp and Heard legal advisers present the role of drugs in their clients’ past relationships, they should not be suggesting that drugs were the underlying reason for bad behaviour.

Drugs can amplify existing feelings and behaviour, but they are not the cause, that much we can be sure of. But as is so often the case, a myth will prove to be far more seductive than fact.

Ian Hamilton lectures in mental health at the Department of Health Sciences, University of York