Clinical depression is frequently misunderstood as simply an intensified version of sadness, but a core diagnostic feature is anhedonia — a loss of interest or pleasure in activities that used to matter to someone, which can occur with or without overwhelming sadness itself. Someone with depression might describe feeling flat, numb, or simply unable to bring themselves to do things they know they'd normally enjoy, rather than crying or expressing grief. This is part of why depression is so often missed, including by the person experiencing it: it doesn't always look like the media portrayal of visible sorrow.
Depression's causes are now understood as multifactorial — biological factors (genetics, neurotransmitter systems, hormonal changes), psychological factors (thought patterns, past trauma), and social factors (isolation, chronic stress, major life changes) all contribute, usually in combination rather than any single cause. This matters practically because it means effective treatment is often also multifactorial: medication addresses biological contributors, therapy addresses psychological patterns, and rebuilding social connection and routine addresses the social dimension — which is why a purely one-track approach (medication alone, or willpower alone) often underperforms combined approaches in research on treatment outcomes.
Frankl, writing from his own experience as a prisoner in Auschwitz and several other camps, describes the specific behavioral marker that veteran prisoners learned to watch for as a sign that someone had psychologically given up. It wasn't crying, or complaining, or any visible expression of sadness — it was a prisoner suddenly smoking through their entire hoarded ration of cigarettes at once, instead of trading them for food as everyone did to survive. Frankl writes: "we knew he had given up faith in his strength to carry on, and, once lost, the will to live seldom returned." The prisoners who endured, in his account, weren't the ones who felt the least despair — they were the ones who kept some future-directed reason to keep going, however small.