For those of us fortunate enough to have good genes, a stable upbringing and happy adulthood the allure of drugs can be hard to grasp. Our brain’s reward systems are replete with healthy and balanced levels of neurotransmitters (chemical messengers) linked to pleasure and motivation like dopamine, opioids and their receptors, ensuring that we derive sufficient pleasure and fulfilment from everyday rewarding experiences – being with friends and loved ones, eating tasty food, exercising, reading a good book, going to the theatre… We may experiment with mind-altering substances out of curiosity every now and then as humans have done for 10,000 years, but most of us feel no need to follow that path regularly and are wary of where it leads.
For others, nature and nurture may not have been so kind; genetic risk factors (related to traits like impulsivity, novelty seeking, high stress reactivity and poor emotion regulation) combined with environmental risks (such as early exposure to drugs, a deprived, chaotic or abusive upbringing, stressful life events) mean that alcohol and drugs are a normal part of life and hold great appeal. The ability of drugs and alcohol to increase brain dopamine levels by 2-10 times that of natural rewards (e.g. food) may be highly tempting to those with sluggish reward systems, giving them the energising, stimulating buzz that otherwise eludes them. In others, the ability of opioids to provide an extraordinary warm rush of pleasure and soothe the psychological pain resulting from years of neglect, abuse or lack of human affection may be too powerful to resist, particularly in the absence of other forms of support.
For some, the process of addiction may involve overactive associative learning - like Pavlov’s dog we learn (to varying degrees) to associate rewards with the places, people, situations and moods which accompany them and in some people these ‘cues’ can become potent triggers of drug craving; grabbing their attention, overwhelming their thoughts and energising their drug-seeking behaviour.
Science can all too readily explain the vicious cycle of addiction because the diverse causes of addiction are unfortunately also consequences of repeated drug use: the opioid and dopamine systems become less sensitive and responsive to everyday pleasures as the brain habituates and adapts to the effects of drugs and the user requires ever-increasing doses to capture the initial high or soothing effect. At the same time, repeated drug use strengthens learnt associations producing ever-more powerful cravings and obsessive focus on the drug when exposed to internal or external drug-related cues. With sufficient use, something akin to a habit may develop with behaviour being ‘automatically’ triggered by these cues.
Drugs may offer short-term relief or pleasure but they change and re-wire the brain in unhelpful ways; weakening our sensitivity to natural rewards, lowering our moods when in withdrawal and strengthening our desire for more drugs. Whilst physiological dependence and unpleasant (or even life-threatening) withdrawal symptoms often characterise addiction, it is formally diagnosed when someone experiences a loss of control over their substance use; when the compulsion to use becomes overwhelming, they can’t reduce their intake and it starts to take over their life, causing them harm or leading them to neglect other interests and activities.
A loss of control is therefore a defining feature of addiction but people vary considerably in how much self-control they have in the first place. Self-control operates at many different levels, from the lofty life goals we set ourselves to our basic ability to suppress an action. The basic ability to inhibit a response can be accurately measured using computerised tests and is associated with the genetic risk for addiction and with people’s ability to resist cravings for food and cigarettes in daily life. Incredibly, after comparing hundreds of identical and non-identical twins, psychologists estimate that this important cognitive ability is ~ 99% heritable. Another form of self-control, delayed gratification (exemplified by Walter Mischel’s famous marshmallow test – eat one now or resist and get two later), is also highly (~50%) heritable and is associated with brain dopamine levels and the development of addiction.
Breaking free from the cycle of addiction is tough. Resisting the urge to drink or take drugs can be a Titanic task; as once a substance has dominated a person’s life to the extent that help is needed, it is usually completely enmeshed in their day to day existence. Once through the detox stage, the addict is commonly left anxious and depressed, partly due to increases in stress hormones. Whether an addict will succeed at remaining abstinent, or fail like the 80% of people who return to alcohol or drug use after detox seems partly determined by the state of their brain. Lower levels of the brain chemical dopamine levels, poor functioning in the frontal areas of the brain and weaker connections between different brain regions have all been show to make someone more likely to relapse.
Most drug treatments for addiction try to either reduce withdrawal symptoms or reduce the pleasure from taking a drug; psychological treatments work on increasing one’s self control and motivations to change. But a surprisingly effective new treatment gets people not to drink, use drugs, or smoke cigarettes by paying them small cash rewards. That former drug users respond so well to these small amounts of money is a counter to the idea that drug use is simply due to a problem in self-control or a sluggish reward system. Rather, for people from deprived backgrounds with histories of abuse, there may simply be few chances for pleasure in their worlds. For these individuals, using drugs may be a choice, rather than a compulsion.
None of us can ever know what it is like to be someone else and experience the world ‘through their brain’. Given the same set of genes and life circumstances we would probably succumb to the same temptations as another; as William Blake said in ‘The Marriage of Heaven and Hell’ (c. 1790-193) “Those who restrain desire do so because theirs is weak enough to be restrained”. Scientific evidence confirms that we are not all equally free to choose our path and resist the lure of drugs. We would therefore do well to avoid judging others and instead view one another with understanding and compassion. Providing addicts with effective psychological and pharmacological treatments and a supportive (rather than punishing) social and physical environment is the best way to help them recover. Addicts need time, space and support to withdraw from drugs and gradually replace old maladaptive associations and patterns of behaviour with new ones.
Natalia Lawrence is a Senior Lecturer in Psychology at the University of Exeter. Her research examines the causes of addictive behaviour, particularly overeating and gambling, and whether computerised cognitive training can improve impulsive behaviour.
Celia Morgan is a Professor of Psychopharmacology at the University of Exeter and researches new treatments for addiction as well as the effects of drug and alcohol when people are intoxicated and in people without drug or alcohol problems.