✶Explainer02:00
Depression as psychic pain: the evolutionary analogy to physical injury
Ed Hagen argues depression is best understood as an extreme form of sadness, or 'psychic pain,' that works like physical pain. Physical pain makes you stop the harmful behavior and think about how to avoid it in future. Psychic pain does the same for social losses — a breakup, a firing, a death — signalling that something is damaging your biological fitness and demands attention.
- Depression's symptoms (sadness, low interest, sleep and appetite changes) are things everyone has felt, unlike schizophrenia's delusions
- Physical pain has two functions: stop the injurious behavior, and learn to avoid the situation later
- Psychic pain is the social analogue — it flags a threat to survival and reproduction
- The framing is drawn from Randy Thornhill, Randy Nesse and Paul Andrews
“We should really think of depression probably as an extreme form of sadness or what Randy Thornhill and others have called psychic pain.”
“It's a signal that you're doing something that is going to harm your biological fitness.”
#depression#evolutionary-psychology#psychic-pain#mental-health
✶Explainer06:30
Adversity is the overwhelming cause of depression
Hagen defines adversity as any situation that decreases your biological fitness — your ability to survive and reproduce. Losing a mate, getting sick or injured, being fired, losing access to resources, or the death of a loved one all qualify. Depression kicks in hardest when the adversity has no obvious solution and requires prolonged, effortful thinking.
- Adversity = anything that reduces your ability to survive and reproduce
- Examples: losing a mate, illness/injury, job loss, natural disaster, death of a loved one
- The evidence for adversity causing depression is described as overwhelming and likely causal
- Depression is worst when the solution isn't obvious and demands heavy cognitive resources
“From an evolutionary perspective, it would be any situation or circumstance that's likely to decrease your biological fitness.”
#adversity#depression#biological-fitness#evolutionary-psychology
✶Explainer13:00
Depression also works as a signal of need to your social partners
Beyond the personal experience of pain, Hagen argues depression has a signalling function. Just as physical injury produces tears, crying and visible distress that summon help, the behavioral shutdown of depression signals to social partners that something is wrong and that you need support you can't provide for yourself.
- Physical injury produces honest signals of need — crying, screaming, facial expressions
- You often can't address adversity alone, so evolved signals recruit help
- Depression's visible manifestations let social partners infer your state of mind
- This is a second evolutionary reason for depression's behavioral symptoms
“Often we can't address adversity completely by ourselves... that's another evolutionary reason why depression does involve some of these impacts on our behavior.”
#signaling#depression#social-support#evolutionary-psychology
✶Explainer17:00
The strength hypothesis: is the sex difference in depression really a strength difference?
Women are about twice as likely to be depressed as men. Hagen's group hypothesised this is really a strength difference, not a sex difference. Because social conflict is deeply intertwined with depression and physically stronger individuals tend to prevail in conflicts, they tested whether controlling for upper body strength would erase the sex gap. Controlling for hand-grip strength, the sex difference in depression diminished and in some analyses disappeared.
- Depression is deeply intertwined with social conflict and anger
- Upper body strength predicts prevailing in physical conflicts; there's almost no male/female overlap
- Controlling for grip strength made the sex difference shrink or vanish
- Stronger people (within and across sexes) are less likely to be depressed
- The effect held after controlling for SES, age, hormones and health status — but it's correlational
“When we controlled for upper body strength, the sex difference in depression diminished and actually went away in some of our analyses.”
“Stronger people are less likely to become depressed and physically weaker people are more likely to be depressed in our data.”
#strength-hypothesis#sex-differences#depression#grip-strength#conflict
✶Explainer24:30
Why the attempt, not the completion, is the real phenomenon of interest
Hagen reframes suicide research around attempts rather than deaths. For men there are roughly 10 attempts per completion; for young women it can be 100 or more. He argues the attempt is the behavior selection is acting on, and deaths are the unintended tail. The sex difference in completions largely reflects method lethality — men more often use guns — rather than a difference in the underlying signal.
- Women attempt suicide far more often; men complete more often
- Roughly 10 attempts per completion in men; up to 100+ in young women
- The attempt rate for both sexes dwarfs the completion rate
- Men's higher completion rate is largely explained by lethal methods like firearms
- China is flagged as a possible exception with high female completion rates (to be verified)
“Really the phenomenon of interest here is the attempt, not the success.”
#suicide#sex-differences#method-lethality#statistics
✶Explainer35:00
Why depression and suicide onset in adolescence: entering mating competition
Depression and suicidal behavior onset in mid-adolescence to early adulthood and peak there, then decline. Hagen ties this to the transition from the protected juvenile phase — where you're shielded by family and not competing for mates or resources — into the adult reproductive phase, when mating and resource competition become intense. Notably, completion rates keep climbing with age even as behaviors fall.
- Onset tracks the shift from juvenile protection to adult reproductive competition
- Behaviors peak in the mid-20s when competition is most intense, then decline
- Completion rates rise with age even as the frequency of attempts falls
- Older people may need costlier, riskier signals and are also more physically vulnerable to dying
“When we see these behaviors onset is right when we're transitioning from the juvenile phase... to the adult reproductive phase, when intense competition can become…”
#age#adolescence#suicide#mating-competition#life-history
✶Explainer41:00
Postpartum depression as a psychic-pain response to missing social support
Hagen's dissertation research examined the paradox of postpartum depression — misery right after reproductive success. His answer: humans are cooperative breeders who never raised children alone, and the strongest correlate of postpartum depression is a lack of social support from a partner or family. Ancestrally, that absence signalled the child might not survive, triggering psychic pain that demands change or, in the harshest conditions, withdrawal of care.
- Humans are cooperative breeders — 'it takes a village' to raise a child
- Lack of social support (from husband or family) is the dominant correlate of postpartum depression
- Ancestrally, absent support was a cue the child wouldn't make it
- Child health problems and pregnancy complications are also strong correlates
- The depression functions as a costly signal that the mother genuinely needs help
“Many many cases of postpartum depression are occurring in contexts where mothers feel they don't have social support.”
#postpartum-depression#cooperative-breeding#social-support#psychic-pain
✶Explainer58:30
Music as a credible signal of coalition quality
Hagen tackles the evolutionary mystery of music by focusing on precise synchronization. Achieving tightly synchronized joint performance takes weeks or months of practice, so a group that performs in perfect synchrony is displaying, in minutes, how coordinated and committed a coalition they are. Observers can rapidly assess whether performers have practiced together for a long time — critical information when groups choose allies for war or food-sharing.
- Precise synchronization is the distinctive, hard-to-fake feature of music
- Ethnographic record shows groups practice songs and dances for weeks before a feast
- A short performance lets observers assess coordination that's otherwise hard to see
- Humans cooperate at the group level, so assessing coalition quality is vital
- Specialized musical memory (recalling old songs in perfect synchrony) supports the adaptation idea
“Precise synchrony could be a signal of coalition quality... the only way that you can achieve that precise synchrony is with a lot of practice.”
#music#credible-signaling#coalition#synchronization#evolutionary-psychology