November 28, 2021

I, Science

The science magazine of Imperial College

Stop! Before you drink that pint, have you considered a genetic test? Susceptibility to developing mental illness from alcohol could come from genes ...


On the last day of my placement the psychiatric consultant told us, jokingly, that her children were banned from alcohol and drugs until at least 25, in light of recent research indicating the brain is still developing until this time.

I have seen a wide range of mental illness in the past two months, and several themes came up time and time again. Events in adolescence. Stress and anxiety. Alcohol. Drugs. Family history. It is hard to dissect cause and effect, because genes predisposing people towards mental illness also predispose them to substance abuse and addiction. Mental illness itself predisposes to substance abuse, and substance abuse predisposes to mental illness. It’s complicated. However, some relationships are clear.

Cannabis and psychosis have a long association, especially in the press. Scientifically the association is exists, but it’s slightly more convoluted. In an adult, for example, cannabis induces a temporary psychosis that wanes as the drug is gradually excreted. In a schizophrenic adult cannabis induces a relapse of schizophrenia that does not wane with the drug; rather it requires anti-psychotics. In adolescents cannabis causes temporary drug-related psychosis, but can also cause physical changes in the frontal lobes of the brain that produce schizophrenia. This still only happens in the genetically susceptible – but if these same people were to avoid cannabis until adulthood, they avoid schizophrenia.

Moulding brains

There is something about adolescent and young brains that makes them very vulnerable to their chemical environment. Like concrete, they can be moulded into any shape while fluid, but once set the shape is permanent. The adolescent brain is at this fluid stage, research now suggests,  until it is 25 years old.

Brains are still maleable up until the age of 25, research suggests…

Right now, scientists are concerned that excessive drinking alcohol during this time window may also result in permanent changes to the brain; something reviewed recently in the journal Cortex.

Alcohol during pregnancy is unadvisable because even small amounts are particularly toxic to the foetus’s central nervous system and brain. Foetal alcohol syndrome is associated with maternal alcohol consumption, involving mental retardation and behavioural difficulties, plus enhanced risk of mental illness later in life.

Acute alcohol intoxication causes changes in blood flow and transmission in particular brain regions –We recognise this as lowered inhibition levels, poor gait co-ordination, impaired decision making and poor memory: getting drunk.. Alcohol can induce full-blown psychosis in susceptible individuals – voices, delusions, hallucinations – and it can trigger both new and recurrent episodes of mental illness. Alcohol withdrawal is one of the few drug withdrawals that is not only gut-wrenchingly unpleasant – patients see snakes and spiders crawling on their skin – but can actually kill you. Heroin withdrawal, in comparison, is unpleasant, but not fatal.

Binge drinking is as damaging as chronic consumption. Notably it is commonest in the exact age groups susceptible to brain damage: adolescents and young adults. In studies on University students binge drinkers performed more poorly in attention tasks, working memory, task switching, planning, information processing, verbal re-call and (for girls especially,) visuospatial tests. Brain imaging showed reduced temporal lobe mass and reduced hippocampal volume. Both of these areas also waste away in adults who have chronically abused alcohol, and they play an important part in memory and cognitive function.

It is known that binge drinking and drinking from a young age are factors that predispose individuals to later-life alcoholic brain disease, but what is less clear is the permanency of the biological damage sustained by adolescent binge drinking. In studies on adolescents addicted to alcohol, even those who had abstained for a long time retained brain deficits. Unfortunately ‘addicted’ sub-groups are a special case, since genetic predisposition to addiction also influences the risk of permanent brain damage – their brains are vulnerable.

Complex connections

Fundamentally, mental illness is clearly associated with frontal regions of the brain, the same areas where drugs exert their mechanisms of effect, and the same areas that undergo tremendous reconstruction during puberty and early adulthood. Alcohol is known to acutely and chronically target these pathways – and adolescents target alcohol. Furthermore they are at the stage where decision-making affects their social, psychological, educational and financial trajectories in life.

All this is thought provoking. It is one of the concerns driving the motion to cull both under age and binge drinking. I have seen the prevalence of alcohol involvement in the inpatient departments of a psychiatric hospital, and the direction these theories are taking doesn’t surprise me. However, there are genetic influences over all that we do; I have acquaintances who live wild lives and only a minority have gone on to be diagnosed with mental illness – triggered, exacerbated or expressed – via alcohol abuse. But it is sad to think there’s a chance, however small, that their illness is a result of a poorly-timed exposure to vodka shots. Maybe in fifty years time our drinking age will be determined by a background genetic check. Either that, or we will all be experiencing a degree of alcoholic dementia for ourselves.

IMAGES: and Gordon, flickr.