Drugs are frequently prescribed for people with emotional and behavioural problems – problems we currently label as ‘depression,’ ‘schizophrenia,’ ‘bipolar disorder’ and ‘ADHD.’ In trying to understand more fully what these drugs actually do to people, I have formulated two different ‘models’ of drug action: the ‘disease-centred’ model, and the ‘drug-centred’ model. The disease-centred model suggests that psychiatric drugs work because they reverse, or partially reverse, the disease or abnormality that gives rise to the symptoms of a particular psychiatric disorder. Thus ‘antipsychotics’ are thought to help to counteract the biological abnormalities that produce the symptoms of psychosis or schizophrenia, ‘antidepressants’ are thought to act on the biological mechanisms that produce symptoms of depression and ‘anxiolytics’ are believed to act on the biological basis of anxiety. ‘Mood stabilisers’ are thought to correct a pathological process that gives rise to the condition of manic depression (bipolar disorder) or, as is sometimes claimed, to variability of mood more generally.

The disease centred model is borrowed from general medicine and presents drugs through the prism of the disease, disorder or constellation of symptoms the drugs are thought to treat. According to this view, drugs have their effects in a diseased or abnormal nervous system. The important effects of drugs are the ones they exert on the disease process. All other effects are of secondary interest and are referred to as ‘side effects’. An example from medicine, one that is often cited by psychiatrists in an effort to re-inforce the disease centred model, is the use of insulin in diabetes. By replacing the body’s failing supply of the hormone insulin, replacement insulin treatment helps to move the body towards a more normal state.  However, even symptomatic treatments like pain killers act in a disease centred way because they produce their effects by counteracting some of the physiological processes that produce pain.

In contrast, the ‘drug-centred’ model suggests that far from correcting an abnormal state, as the disease model suggests, psychiatric drugs induce an abnormal or altered state. Psychiatric drugs are psychoactive substances, like alcohol and heroin. Psychoactive substances modify the way the brain functions and by doing so produce alterations in thinking, feeling and behaviour. Psychoactive drugs exert their effects in anyone who takes them regardless of whether or not they have a mental condition. Different psychoactive substances produce different effects, however. The drug-centred model suggests that the psychoactive effects produced by some drugs can be useful therapeutically in some situations. They don’t do this in the way the disease-centred model suggests by normalising brain function. They do it by creating an abnormal or altered brain state that suppresses or replaces the manifestations of mental and behavioural problems.

Alternative Models of Drug Action

An accepted example of the drug centred model is the proposed benefits of alcohol in people who experience social phobia or social anxiety. Alcohol helps to reduce social anxiety not because it corrects an underlying biochemical imbalance, but because features of alcohol induced intoxication include relaxation and disinhibition. It is the superimposed state of intoxication itself that helps, not the effects of the drug on a disease mechanism.

Another interesting example is the use of opiate pain killers, such as morphine. Opiates exert a direct ‘disease-centred’ effect by slowing the conduction of messages in the pain nerves, but they also have well-recognised psychoactive effects. They induce a characteristic altered state in which people become emotionally detached or indifferent- sometimes this is referred to as ‘emotional anaesthesia’. People who have taken opiates for pain often say that they still have some pain, but they don’t care about it anymore. This is a ‘drug-centred’ effect in as much as it demonstrates the overlaying of the experience of pain by a drug-induced alteration in emotional experience.

When modern psychiatric drugs were introduced in the 1950s, they were understood according to a drug-centred model. Antipsychotics, for example, which were then known as ‘major tranquilisers,’ were regarded as a special sort of sedative. They were thought to have properties that made them uniquely useful in situations like an acute psychotic episode, because they could slow up thought and dampen emotion without simply inducing sleep, but they were not regarded as a disease-targeting treatment. By the 1970s, however, this view was eclipsed and the disease-centred model of drug action became dominant. Accordingly psychiatric drugs were regarded as specific treatments that worked by targeting an underlying disease or abnormality.  The change is demonstrated most clearly in the way drugs have come to be named and classified. Prior to the 1950s drugs were classified according to the nature of the psychoactive effects they produce. Existing drugs were crudely classified as having either sedative or stimulant effects on the nervous system. After the 1950s, however, drugs came to be named and classified according to the disease or disorder they are thought to treat; antidepressants, antipsychotics and anxiolytics, for example.

The ascendance of the disease-centred model of drug action did not occur because of overwhelming evidence of the superiority and truth of the disease-centred model. There was not then, and is not now, convincing evidence that any class of psychiatric drugs has a disease centred or disease-specific action. There was not even any real debate about alternative theories of drug action. The disease centred model just took over and the drug-centred view simply faded away. People forgot there had ever been another way of understanding how psychiatric drugs might work.

My work has focused on rehabilitating the drug-centred view of drug action because I believe it is the correct way of understanding what the drugs we currently use are doing when they are taken by people diagnosed with mental health problems (and anyone else for that matter). The drug-centred model demands a more thorough understanding of the total range of effects that drugs produce and starts from the point of view that all drugs are foreign chemicals that necessarily change the way the body normally functions. The drug-centred model focuses our attention on the impact that drugs have on the body and the brain, and on all the possible consequences that drug-induced alterations can have on how people think, feel and behave. It is a necessary starting point for the sensible, cautious and safe use of drugs in mental health services.