A really fascinating study has just come out of Germany: Scientists there think they may have discovered the cause of OCD behaviors in mice.
The scientists found that mice who groom excessively and show other OCD-like behavior are short of a protein called SPRED2 that normally inhibits signals along the chain of proteins that make up the Ras/ERK-MAP kinase cascade. Without that protein, the signals go into overdrive.
The mice, like many humans with OCD (including me), could be successfully treated with SSRIs.
Since SPRED2 is normally found in the basal ganglia and amygdala – which influence action selection and emotional regulation respectively – it’s easy to see why this could play a role in human OCD, too.
It’s still early days, and research has to go beyond just mice, of course. But this could be really, really promising for those of us who have OCD that is not controlled by exposure and response prevention therapy alone. It could also help those of us with mood disorders that react negatively to SSRIs. And, of course, it could also help people with OCD who are not helped by any current therapies.
If humans with OCD show the same protein deficiency as mice, that opens the door to a whole new realm of potential treatments, including one that already exists.
It turns out that a completely different defect on the MAPK-ERK pathway has been linked to certain cancers. Scientists have already developed drugs that slow or block signals along that pathway and are investigating them as potential cancer treatments. One is the drug selumetinib, which is being tested for human use as a therapy for certain thyroid cancers.
What use could a cancer drug have for a person with OCD? Well, according to the German study:
Using the MEK inhibitor selumetinib, we suppressed TrkB/ERK-MAPK pathway activity in vivo and reduced OCD-like grooming in SPRED2 KO mice.
In other words, if humans with OCD show the same SPRED2 deficiency that mice with OCD-like behaviors have, there’s already a drug out there that could help, and it’s already in human trials. It would still need to be tested in OCD-specific trials, but that’s a huge head start.
Other genes on the MAPK-ERK pathway have been linked to schizophrenia, schizoaffective disorder, bipolar disorder and migraines. More research into the proteins that affect the brain and how this pathway works could be beneficial far beyond the OCD world.