High insulin levels in early childhood may be a risk factor for depression and other mental health problems in later life, scientists believe.
UK researchers said they have found a link between persistently high insulin levels from mid-childhood and a higher chance of developing psychosis in adulthood.
The team said their findings, published in the journal Jama Psychiatry, suggest early signs of physical health problems could be present long before the development of symptoms of psychosis or depression.
The experts also believe the link between physical and mental illness to be more complex than previously thought.
Lead author Dr Benjamin Perry, from the Department of Psychiatry at Cambridge University, said: “The general assumption in the past has been that some people with psychosis and depression might be more likely to have a poor diet and lower levels of physical exercise, so any adverse physical health problems are a result of the mental disorder, or the treatment for it.
“In essence, the received wisdom is that the mental disorder comes first.
“But we’ve found that this isn’t necessarily the case, and, for some individuals, it may be the other way around, suggesting that physical health problems detectable from childhood might be risk factors for adult psychosis and depression.”
However, the researchers warned their results do not suggest that childhood insulin levels can predict the likelihood of developing mental disorders in later life.
This is because there are many other risk factors, such as genetic and environmental, that are associated with psychosis.
They recommend healthcare professionals should carry out robust physical assessments of young people who present with symptoms of psychosis or depression, so early signs of physical illnesses may be diagnosed and treated promptly.
Dr Perry said: “These findings are an important reminder that all young people presenting with mental health problems should be offered a full and comprehensive assessment of their physical health in tandem with their mental health.
“Intervening early is the best way to reduce the mortality gap sadly faced by people with mental disorders like depression and psychosis.”
For their study, the researchers used data from the Avon Longitudinal Study of Parents and Children (Alspac), a long-term birth cohort study set in the west of England.
They analysed data from more than 10,000 people to study whether insulin levels and body mass index (BMI) in childhood may be linked with depression and psychosis in young adulthood.
They discovered that disruption to insulin levels can be detected in childhood, long before the onset of psychosis.
This, they said, suggests that some people with psychosis may have an inherent susceptibility to developing diabetes.
The team also found found that a BMI increase around the onset of puberty was linked with a higher chance of developing depression in adulthood, particularly in girls.
Dr Perry said: “The next step will be to work out exactly why persistently high insulin levels from childhood increase the risk of psychosis in adulthood, and why increases in BMI around the age of puberty increase the risk of depression in adulthood.
“Doing so could pave the way for better preventative measures and the potential for new treatment targets.”