This claim is patently false.
The “21 times” figure is fabricated, and the framing is scientifically inaccurate
The claim from Adam Lane Smith (
@AdamLaneSmith) contains two specific assertions: that sex gives “1 hit” of dopamine and that intense pornography gives “21 times” the dopamine from sex. Neither is supported by neuroscience.
The “21 times” number doesn’t exist in any research
No peer-reviewed study has ever measured dopamine release from pornography at 21 times that of sex. The figure does not appear in any neuroscience literature. It appears to be invented or badly garbled from another source.
The actual quantified comparison that exists in neuroscience is between natural rewards and drugs — not between sex and porn. Natural rewards (including sex, food, social bonding) increase dopamine levels by as much as ~100% above baseline, while drugs like cocaine can spike dopamine by as much as ~1,000% — roughly a 10:1 ratio, not 21:1. Pornography is not a drug and has never been shown to produce drug-level dopamine surges.
Direct measurements essentially don’t exist. Direct dopamine measurements in humans during sexual activity or pornography viewing are extremely rare. Most studies use proxies like fMRI or blood flow imaging, which cannot produce the kind of precise quantitative comparison the claim requires. The available evidence suggests dopamine levels during masturbation or porn use are “comparable to normal sexual activity,” though this too is described as plausible rather than directly measured.
Dopamine is misunderstood in the claim. The tweet treats dopamine as a simple “pleasure chemical” where more = more pleasure = more addiction. This is a popular misconception. Dopamine is primarily involved in motivation, prediction, and learning — it rises during anticipation of reward, not just during pleasure itself. High dopamine release from sexual stimuli does not automatically equal addiction.
The “dopamine receptor burnout” hypothesis is weak. A PET imaging study found no evidence of reduced dopamine D₂/₃ receptor availability in compulsive pornography users compared to controls — directly undermining the “receptor burnout” idea underlying the addiction framing. Some neuroimaging studies have found correlations between problematic porn use and altered reward-circuit activity, but these are associations, not proof of causation or damage.