Oh yeah, I’m unhappy again (Image: KPA/Zuma/Rex Features)

Daydreaming seems to be bad for your mental health, say the psychologists who used an iPhone app to track the moods of more than 2000 people.

The app let the researchers do something that traditional psychology methods do not: intrude on people’s lives on a regular basis. Around three times a day, the software prompts users to answer questions about what they are doing and feeling. It also asks users to say whether they are focusing on whatever task is at hand, or if their mind is wandering.

Mind-wandering turns out to be extremely common – users reported daydreaming almost 50 per cent of the time. The state occurred most frequently while people were brushing their teeth or doing other grooming. During only one activity – making love – did the frequency of mind-wandering drop below 30 per cent.


App users were also more likely to report feeling unhappy when their mind was wandering. Crucially, episodes of mind-wandering tended to precede bouts of low mood, but not vice versa, suggesting that the former caused the latter.

“That’s the biggest take-home,” says Matthew Killingsworth of Harvard University, who conducted the study with his colleague Daniel Gilbert. “Mind-wandering might be something that is damaging to people’s happiness.”

Sad bias

The link may be due to an asymmetry in how daydreams affect mood. Killingsworth and Gilbert found that daydreams about pleasant things were linked to improvements in mood, but only slight improvements. Thinking about neutral topics while mind-wandering was linked to a similarly modest drop in happiness, but daydreams about unpleasant topics coincided with a 20-point drop on the 100-point scale that app users used to rate their mood.

“This is a really solid piece of work,” says Jonathan Smallwood at the University of California, Santa Barbara. He says that mind-wandering and levels of happiness have been linked in laboratory studies, but never before in such a large population of people going about their daily lives.

But the claim that mind-wandering causes unhappiness needs to be further evaluated, he adds, because he and others have shown the effect can run in the opposite direction. In laboratory experiments, he found that lowering a person’s mood, perhaps by showing them a video about a sad story, led to more mind-wandering.

“It’s difficult to make causal claims,” says Smallwood. “But it’s undoubtedly the case that negative mood and mind-wandering are inextricably linked.”

The connection suggests that cutting down on mind-wandering, either by practising meditation or simply by keeping busy, could help people battle depression. Cutting out daydreaming altogether, even if that were possible, is not recommended, though: “The irony is that mind-wandering also underlies invention,” says Smallwood. “We don’t want to tell people not to do it.”

Journal reference: Science, DOI: 10.1126/science.1192439