A new study has revealed two patterns of symptoms that could be used to predict the development of bipolar disorder in young people.
These findings could potentially give us a better early warning system for the mental health condition that causes extreme mood swings and is notoriously difficult to diagnose.
We don't know exactly what's behind bipolar disorder (BD), though a number of environmental and genetic factors are thought to be involved; up until now we haven't had much data on the kind of behaviour that can eventually build up to BD either.
To try and improve our knowledge of any potential "prodromal" symptoms, or symptoms appearing before bipolar disorder itself shows up, the international team of researchers looked at 39 previous studies of prodromal symptoms and risk factors for BP, sifting through the findings to see if any patterns emerged – and two did.
"There was evidence of a wide range of psychopathological symptoms, behavioural changes, and exposures with statistically significant associations with later diagnoses of BD," report the researchers in their paper.
"Some of these factors anticipated syndromal onset of BD by years."
The first pattern of symptoms the researchers spotted was homotypic – that is, similar to BD itself. These symptoms include mood swings, periods of excitability, and major depression, which look almost like bipolar disorder but still fall short of the full condition.
These symptoms were described as "low sensitivity", which means that most young people with these symptoms didn't go on to develop bipolar disorder.
However, they had "moderate to high specificity", meaning the symptoms did appear in many of those who were eventually diagnosed with the condition.
The second pattern of symptoms was heterotypic, meaning they were different to bipolar disorder itself. Here the list included anxiety, attention disorders, and behavioural disorders such as attention deficit hyperactivity disorder.
Both sensitivity and specificity were low in this case, so relatively few young people with these symptoms went on to develop bipolar disorder, and of those who did end up with the diagnosis, relatively few had these symptoms early on.
In all the studies that the researchers looked at, these symptoms had been recorded before BD was diagnosed.
And while the findings fall short of a completely accurate early warning system for bipolar disorder, they do hint that some early signs might be there if we look close enough.
The analysis also turned up some risk factors for BD that have been spotted in studies before, including head injuries, exposure to drugs, physical or sexual abuse, stress, and preterm birth.
And while knowing that someone is at risk of BD isn't yet enough for doctors to stop it from developing, it could be crucial in managing the condition from the onset, or in finding ways that it could be avoided further down the line.
Both Bipolar I Disorder, involving extended manic episodes, and the less severe Bipolar II Disorder were covered by the analysis. These conditions affect around 3 in 100 adults every year and usually develop between the ages of 15 and 19.
What the new research gives us is a good base for future studies into how bipolar disorder could develop and which young people might be at risk, as well as a better understanding of how these different symptoms relate to each other.
"In order to enhance the prognostic value of clinical features that can predict later diagnosis of BD, it may be necessary to combine multiple risk factors rather than to focus on single predictors," conclude the researchers.
"It also remains to be explored whether different features or clusters of factors may have specific predictive value for particular aspects of BD."
The research has been published in the Harvard Review of Psychiatry.