> Depressed people move more slowly, in a characteristic pattern called “psychomotor retardation”. They display perceptual abnormalities. They’re more likely to get sick. There are lots of results like this.

> Depression has to be about something more than just beliefs; it has to be something fundamental to the nervous system.

Depression is frequently related to metabolic problems: people are exhausted because their mitochondria aren't putting out enough ATP to run their nervous system.

There are various interventions that can help. B-vitamins are important cofactors for burning sugar to make energy. T4 thyroid is activated by the liver to make T3, which is one factor that boosts the metabolism. If the liver is overworked (alcohol, drugs, hormonal imbalance, too much pufa, etc), it can have trouble activating adequate thyroid.

Emotional resiliency is a big factor here too. My friend was really just lonely before she met me. She's doing better now because she now has a 'vision' for her future (she originally 'lost her future' when she was expelled from high school, essentially for being depressed and self-medicating with drugs that are now being investigated for treating depression).