La depresión endógena existe pero es rara y casi siempre se da en viejos. Los psicólogos mediocres lo diagnostican cuando no quieren perder mucho tiempo con un paciente a pesar de que sea endógena o adaptativo ambos necesitan un gatillante externo.

> Endogenous depression was initially considered valuable as a means of diagnostic differentiation with reactive depression. While the latter's onset could be attributed to adverse life events and treated with talk therapy, the former would indicate treatment with antidepressants. Indeed, this view of endogenous depression is at the root of the popular view that mood disorders are a reflection of a 'chemical imbalance' in the brain. More recent research has shown that the probability of an endogenous depression patient experiencing an adverse life event prior to a depressive episode is roughly the same as for a reactive depression patient and the efficacy of antidepressant therapy bears no statistical correlation with the patient's diagnostic classification along this axis.
https://doi.org/10.1037%2F0022-006x.61.5.858
https://pubmed.ncbi.nlm.nih.gov/8245283