Addiction and brain injury

It is a real pleasure to be asked to give this talk. I will start off by saying that I'm not a clinician myself and I don't work directly in addiction, but my work addresses issues to do with addiction, and I am now beginning to do research in the area.

As an overview, I'm going to look at stereotypical attitudes about addiction, what addiction is, and what pleasure is. Addiction is the loss of control over these pleasurable activities. That will allow me to talk a tiny bit about brain networks and addiction, which will lead into the topic of addiction following different types of brain injury, both in adults and children. I'll briefly talk about therapies, as I know that is an important issue, and then I'm going to end with a twist in the tale which is rather interesting.

I always like to start with what the layperson in the street thinks about addiction. There is a classic, visceral image of someone struggling with substance use. However, we are beginning to understand more and more that there are behavioral addictions, such as internet use or the need to spend money on things you don't really need. It is important to realize that addiction is not just about drug use; it is about pleasurable activities that may eventually result in someone not being able to control themselves very well.

The NHS defines addiction as not having control over doing, taking, or using something to the point where it could be harmful to you. The issue isn't the substance itself, whether it's smoking, drinking, or drugs; it's the loss of control and the potential harm.

To understand why this happens, we can look at a simplistic diagram of the brain. Very simplistically, we have three brains in one: the Reptilian Brain for instincts and urges; the emotional limbic brain which gives us pleasure and motivation; and the walnutty bit on the outside, known as the decision-making neocortex. While all animals have these, the human neocortex is particularly developed.

We get a lot of insight into the function of the prefrontal cortex from the famous 1800s case of Phineas Gage, who survived an iron bar passing through his head. While he initially seemed unchanged, he eventually became extremely unreliable, unable to make decisions, and socially uncouth. Over 150 years later, a patient with a brain tumor showed remarkably similar problems after surgery damaged the same frontal area. These cases highlight the importance of the front of the brain for controlling our behavior and decision-making.

Addiction is rooted in pleasure. Scientists identified the brain's pleasure center—the ventral tegmental area (VTA)—by stimulating it in rats, which caused them to continuously perform an action to receive a reward. This area is stimulated by natural activities like eating or sex, but also by addictive drugs like opiates, cocaine, and nicotine. In a healthy system, the VTA is linked to the nucleus accumbens and the prefrontal cortex, which acts as a control mechanism, allowing us to enjoy pleasures while knowing when to stop. In addiction, that circuitry becomes maladaptive; the control mechanism is no longer working, leading to a cycle of wanting more and more.

Regarding substance use disorder, up to 60 percent of people requiring inpatient rehab for brain injury may have had prior problems with alcohol or drugs. Intoxication also predisposes people to brain injury due to poor decision-making or being at greater risk of victimization. Post-traumatic brain injury, data suggests that 10 to 20 percent of people develop a substance use disorder for the first time, even if they were abstainers or light drinkers before.

It is also important to consider the developing brain. Different parts of the brain mature at different times, with the front of the brain not fully functional until the mid-20s. Adolescence is a danger zone for substance use because the decision-making part of the brain is not yet fully mature. When a brain is damaged in childhood, it never really catches up to the level of an uninjured brain, often leading to behavioral problems.

Longitudinal studies in New Zealand, Taiwan, and Canada have shown that childhood brain injury increases the likelihood of alcohol dependence during adolescence. There are also indirect effects, as brain injury can limit protective factors like finishing school or being employed, while increasing risky behaviors and alienation from family and peers.

In terms of treatment, community-based approaches are necessary as residential options are often unavailable. While motivational interviewing in isolation has limited success, skill-based interventions show more promise. Treatment is most effective when it combines individual and group psychotherapy. However, we must be cautious, as dropout rates from addiction rehab are very high.

Finally, there is a twist in the tale: some studies show that damage to the basal ganglia and the insula can actually reduce addiction, such as smoking. While this isn't a strategy for helping those with brain injury, it holds promise for future therapy, perhaps by using stimulation techniques in those areas to help people with substance use disorders.

In my own research, I use an assessment of executive function—the ability of the front of the brain—via a role-playing computer task. It has shown the ability to pick up difficulties in people with brain injury and, more recently, in patients with substance use disorders, which may help in tailoring future therapies.

To summarize, addiction is complex and involves a loss of control. Traumatic brain injury can cause or worsen addiction due to damage in the front of the brain, combined with psychosocial and emotional issues. Severity of injury, pre-existing history, and the timing of the injury during development are all critical factors. While there is no easy fix, research is beginning to uncover the mechanisms necessary for effective treatment.