Ketamine – “special K” – can break treatment-resistant depression.

Nature has more on how the veterinary tranquilizer-slash-rave drug can reverse “anhedonia” (the inability to feel happy) for 14 days – long enough to bust sufferers out of otherwise untreatable bipolar depression:

The present study used a randomized, placebo-controlled, double-blind crossover design to examine whether a single ketamine infusion could reduce anhedonia levels in 36 patients with treatment-resistant bipolar depression. The study also used positron emission tomography imaging in a subset of patients to explore the neurobiological mechanisms underpinning ketamine’s anti-anhedonic effects. We found that ketamine rapidly reduced the levels of anhedonia. Furthermore, this reduction occurred independently from reductions in general depressive symptoms.

“Positron emission tomography imaging” is a fancy way to say “PET scan.” They were looking inside people’s brains. And what they found…

Anti-anhedonic effects were specifically related to increased glucose metabolism in the dorsal anterior cingulate cortex and putamen. Our study emphasizes the importance of the glutamatergic system in treatment-refractory bipolar depression, particularly in the treatment of symptoms such as anhedonia.

…In other words, they know what parts of the brain are responsible for the effect. They know how the happiness happens.

Found on reddit, where there’s more of a discussion.