Do Smart People Stay Up Later? IQ, Sleep, Drugs and Sex Studies

Short answer: yes, on average, but only by a little. In a large American sample, teenagers who scored higher on a vocabulary-based IQ test went to bed somewhat later as young adults, by roughly half an hour on weeknights when the brightest and the lowest-scoring groups are compared. Separate British data link higher childhood test scores with a greater chance of trying illegal drugs later in life. A third claim, about Oxford and Cambridge students and sex toys, comes from shop sales figures rather than science.

None of this means clever people are destined to be night owls, drug users or anything else. The links are real enough to be interesting and small enough to say almost nothing about any single person. Below is what each piece of evidence actually measured, where it came from, and how much weight it can carry.

The popular picture of a clever person

Ask people to picture a highly intelligent person and most will describe someone disciplined and a little dull: early to bed, careful with their health, buried in books. The research that circulated widely in 2015 under headlines about smart people staying up late, taking drugs and having more sex was popular precisely because it turned that image upside down.

Most of that research traces back to one scientist, the evolutionary psychologist Satoshi Kanazawa of the London School of Economics, and to his idea that intelligence helps people adopt behaviour that would have been unfamiliar to our distant ancestors. Knowing that background helps when you read the results, because the same theory was used to explain all three findings.

Study one: IQ and bedtime

The sleep finding comes from a 2009 paper by Kanazawa and Kaja Perina titled “Why night owls are more intelligent”, published in the peer-reviewed journal Personality and Individual Differences. The authors used Add Health, a long-running survey of American adolescents. Intelligence was measured in 1994–95 with a picture vocabulary test, and the same people reported their usual sleep times about seven years later, when they were 18 to 28.

The pattern was consistent. Average weeknight bedtimes ranged from about 23:41 in the lowest-scoring group to about 00:29 in the highest. On weekends the gap was wider, from around 00:35 to 01:44. Weekday wake-up times differed by about half an hour, while the difference in weekend wake-up times was not statistically significant.

How big is the effect?

Small. Each extra IQ point predicted less than one minute of later bedtime, and childhood IQ explained only a few percent of the differences in sleep timing between people. With a sample of more than 10,000, even modest associations pass statistical tests. The authors themselves noted that their test measured verbal ability rather than general intelligence and that sleep times were self-reported.

Other research points the same way. A meta-analysis summarised on Wikipedia’s chronotype entry found a small positive association between an evening preference and intelligence. Chronotype is also partly inherited, shifts later in adolescence and earlier in older age, and is shaped by light, meals and school or work schedules, so intelligence is at most one minor ingredient.

Study two: intelligence and drug use

The drug claim has several sources that are often blurred together. The first was not a formal study but a 2010 Psychology Today blog post in which Kanazawa analysed the National Child Development Study, a British cohort of people born in 1958. Intelligence was measured before age 16 and drug use was recorded at 42. In that data the link was steady: the brightest group reported more use of psychoactive drugs than the least bright, even after controlling for social class at birth, parents’ education, earnings and other factors. In his American data, however, the association disappeared once social and demographic factors were taken into account.

Two peer-reviewed papers by James White, G. David Batty and colleagues then examined the question more carefully. One, in the Journal of Epidemiology and Community Health (2012), followed the 1970 British Cohort Study and found that higher childhood IQ was associated with a greater likelihood of illegal drug use in adulthood, with stronger associations in women than in men. The other, in the Annals of Epidemiology (2012), looked at the 1958 cohort in middle age and reported a similar but weaker pattern.

What the drug findings do not say

These studies count whether people had ever used or recently used a substance, which mostly captures occasional experimentation such as cannabis. They do not show that intelligent people are more likely to become dependent. The researchers suggested explanations such as openness to new experiences or the social circles that come with university, but those ideas were not tested directly. If you are worried about your own or someone else’s use, talk to a doctor.

The “sex” claim: Oxbridge and sex toys

The third headline is the weakest. It rests on a 2013 newspaper report in The Telegraph that students at Oxford and Cambridge reportedly spent more on sex toys than students at other British universities. As far as we could check, the figures came from retail sales data, not from a scientific study of intelligence or sexual behaviour.

Spending on a product says little about how often people have sex or how much they want it. It may reflect income, delivery addresses, marketing or simply which students were willing to order online. The suggestion that stressed students use sex to unwind was commentary, not a measured result. So the popular line that intelligent people “have more sex” is not supported by this source.

The theory behind all three: evolutionary novelty

Kanazawa explains these findings with what he calls the savanna-IQ interaction hypothesis. The idea is that general intelligence evolved to solve unfamiliar problems, so more intelligent people should be more willing to adopt values and habits that were rare in ancestral environments. Staying awake long after dark, using refined psychoactive substances and, in his 2010 paper, holding liberal or atheist views were all presented as examples.

The hypothesis is creative but contested. One obvious objection is that early humans almost certainly spent evenings awake around fires, and it is hard to test a notion of “novelty” that can be stretched to fit many behaviours. His 2006 work on intelligence and health drew published criticism for flawed assumptions and biased interpretation. Kanazawa is also a controversial figure: in 2011 the LSE found that a separate blog post of his had brought the school into disrepute, and dozens of evolutionary psychologists publicly distanced the field from his methods, as described on Wikipedia. That does not make every dataset he analysed wrong, but it is good reason to look for independent confirmation, as the White and Batty papers provide for drug use.

Reading studies like these sensibly

• Averages are not destinies. Plenty of brilliant people rise at dawn, never touch drugs and lead quiet private lives.
• Correlation is not cause. Staying up late does not make you smarter, and trying drugs certainly does not.
• Look at effect sizes. “Significant” in a study of thousands can mean minutes, not hours.
• Check the source. A peer-reviewed cohort study, a blog analysis and shop sales figures deserve very different levels of trust.

If you are a natural night owl, the most useful takeaway is practical rather than flattering: consistent sleep matters more than when you sleep, and evening types have been linked with higher rates of low mood, so protecting enough rest is worth the effort. If late nights are leaving you exhausted or low, talk to a doctor.

What do you make of these links? Do the clever people you know keep late hours, or does the stereotype of the early-rising scholar still fit better?

Sources: Kanazawa & Perina (2009), Personality and Individual Differences; Kanazawa, Psychology Today (2010); White, Gale & Batty (2012), J Epidemiol Community Health; White & Batty (2012), Annals of Epidemiology; Wikipedia: Chronotype; Wikipedia: Satoshi Kanazawa; original roundup via The Mind Unleashed.

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