An exhaustive study of more than 20,000 people shows that higher-than-normal body temperature is consistently found in people who suffer strong symptoms of clinical depression.
There may not be a simple solution, like the suggested sauna or hot tub, but what I think this study shows is that there is very clearly something going on physically with depression. This is not an “it’s all in your head” situation, and I hope that perhaps information like this, which shows a measured physical symptom tied to depression, gets us to consider depression as something similar to other physical ailments.
Maybe we could also stop telling people “just to be happy” in response. That would be a good start.