A team of British and American researchers have taken another step forward in the fight against manic depression with the discovery that people suffering from the disorder have a distinct chemical signature in their brains.
The researchers from Imperial College London, the University of Cambridge, and the National Institutes of Mental Health in the US say that the discovery may also indicate how the mood stabilisers used to treat the disorder counteract the changes in the brain that it appears to cause.
Manic depression, also known as bipolar disorder, is a debilitating psychiatric condition characterised by alternating mania and depression, affecting about one in every hundred people worldwide.
Though mood-stabilising drugs lithium and valproic acid are relatively effective when it comes to treating the disorder, doctors have long since wondered why these treatments work are poorly understood.
As part of the study, the team compared postmortem brain tissue samples of people with manic depression with those of age and gender matched controls, taking samples from the dorsolateral prefrontal cortex, which controls the processes involved in higher cognitive functioning.
These samples were then analysed using Nuclear Magnetic Resonance spectroscopy.
The boffins found that people with manic depression had different concentrations of chemicals in dorsolateral prefrontal cortex of the brain than those without.
Using mice, they then checked for the effects of lithium and valproic acid and found that these drugs caused the opposite chemical changes to those seen in the bipolar brain tissue samples.
Chemicals that were increased in the bipolar brain tissue were decreased in rats given the mood stabilising drugs, and vice versa.
Based on their results, the researchers now believe that an upset in the balance of different neurotransmitters known as excitatory and inhibitory neurotransmitters, which are involved in sending signals in the brain, may be central to the disorder.
The study also suggests that lithium and valproic acid work by restoring the balance of these neurotransmitters in the brain.
"By identifying a distinct biochemical profile in patients with bipolar disorder, our new research provides a valuable insight into the origins and causes of the disease. Moreover, the changes we see in people's metabolic signatures may give a target for drug therapy, allowing us to see how effective a drug is at correcting these changes," said Dr Tsz Tsang, one of the authors of the study from the Department of Biomolecular Medicine at Imperial College London.
"In this instance, we have already shown that the biochemical changes which valproic acid and lithium bring about in mammalian models represent almost a mirror image of the perturbations in bipolar disorder. This may provide a useful insight to the actions of these treatments and a basis for which to improve therapy in the future," added Dr Tsang.
The research is published in the journal Molecular Psychiatry.