On a more microscale, depression is associated  with a few things: the abnormal transmission or depletion of certain neurotransmitters, especially serotonin, norepinephrine, and dopamine, blunted circadian rhythms, or specific changes in the REM and slow-wave parts of your sleep cycle, and hormone abnormalities, such as high cortisol and deregulation of thyroid hormones.
Na više mikro, depresija utječe na abnormalne prijenose ili brisanja određenih neurotransmitera, posebno serotonina, norepinefrina, i dopamina, otupjelih cirkadijurnih ritmova, ili posebnih promjena u REM-u  te u fazi sporih valova ciklusa spavanja, i hormonskih abnormalnosti, kao što su visoki kortizol i deregulacija hormona štitnjače.