One of the most common questions about mental health problems: is it just a chemical imbalance in the brain? To give a reliable answer we need to go beyond measuring the uptake of neurotransmitters in particular brain regions. We need to combine accounts from people (sufferers and voluntary subjects) with an understanding of drugs and how they behave in our bodies, and also how our brains react (or not) to drugs, especially by observing changes during live brain scans.
My father, who died over 20 years ago, suffered in his last year from a degree of dementia; this was never properly diagnosed but it seemed more like Parkinson’s disease than any other condition. He may have had a series of mini-strokes in one of the regions of his brain controlling movement. In particular we were astonished when he told us he had seen a dog
in the house, when we were certain there had been no dog. My father didn’t doubt he had seen a dog – it wasn’t like a dream. We later learned that such hallucinations are not uncommon in Parkinson’s patients.
I read very recently about Mitul Mehta’s work in London investigating the ways in which drugs actually affect the mind and brain. His team used psilocybin, a hallucinogenic drug, to simulate hallucinations. They knew that there can be an increase in the 5-HT2A receptors in the visual pathways in Parkinson’s patients suffering visual hallucinations. They also knew of a drug developed for cancer treatment that reduces the effects of 5-HT2A stimulation. Could the cancer drug help the Parkinson’s patients? Volunteers were given the cancer drug, put into a scanner then given psylocibin. It reduced the hallucinations. Later actual Parkinson’s patients were given the drug for 2 weeks; their reactions were monitored and they were also scanned to try and find changes in their visual processing pathways.
Most drugs used to treat mental health conditions were developed before scanners were available. Mehta believes that it is now time to open new windows on how our brains respond to such drugs using scanners as part of controlled experiments, and hopefully point the way to better medications. Eventually we may have better answers to those tough questions, by altering medications, seeing directly how they change the brain, and asking
patients what their experiences were.
Dr Tim Bunn,
New Scientist 13.06.20