Habits, compulsion and addiction

How ordinary habits form, why some become compulsive, and where the science of addiction applies to everyday behaviour and where it does not.

Definitive answers

• ExplainerBWhy do some habits become compulsive?A habit and a compulsion both run through dopamine, but a shift in which brain circuit is in charge — not overstimulation — is what the human evidence shows.
• ExplainerAWhat role does dopamine play in addiction?Human brain-imaging studies show a consistent dopamine signature in addiction — but it is reduced receptor availability over time, not a simple excess.

Claims we have checked

• Dopamine CheckedCDoes porn rewire your dopamine system?Compulsive pornography use shows brain-imaging changes in cue response, but no human study has measured a dopamine change directly.

In the Dopamine Index

• IndexBMusicOne landmark PET study found music can release dopamine in the brain’s striatum, with different regions active during anticipation and peak pleasure.
• IndexDSexRat studies show clear dopamine release during sexual behaviour; human studies use blood-flow scans, not direct dopamine measurement.
• Index?ShoppingThe closest dopamine evidence for shopping comes from a mixed Parkinson’s disease patient group; no study has isolated buying behaviour on its own.
• IndexBNicotineWhat human PET studies actually show about nicotine and dopamine release, and where the popular story overreaches.
• IndexAAlcoholWhat human PET studies show about alcohol and striatal dopamine release, including dose and expectation effects.
• IndexCCannabisWhat human neuroimaging shows about cannabis and dopamine, including the counterintuitive finding in regular users.
• IndexCGamblingDirect dopamine evidence for gambling disorder is small, but Parkinson’s medication offers the clearest causal proof dopamine drugs can trigger it.
• IndexCPornographyCompulsive pornography use shows a cue-response brain pattern in imaging studies, but no human study has measured dopamine itself.
• IndexCLoveEarly-stage romantic love activates dopamine-rich reward regions in fMRI studies; prairie vole research shows dopamine and oxytocin directly drive pair bonding.

How we grade evidence: the dopamine.co.uk Evidence Standard. Try the free tools.

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