Daydreaming is thought to be one of the triggers for invention. But a recent study by two Harvard researchers Matthew Killings worth and Daniel Gilbert, show that it has adverse effects on the mental health of people.

"That's the biggest take-home," says Matthew Killingworth. "Mind-wandering might be something that is damaging to people's happiness."

The research using iPhone apps show that mind wandering causes directly affects the mood of a person. Day dreaming about positive things may improve the happiness quotient a little, but dreaming about unpleasant things causes a 20 percent dip. “This is a really solid piece of work," says Jonathan Smallwood at the University of California, Santa Barbara.

Daydreaming or mind wandering is very common and there have been studies on daydreaming and its effects on human mood in the past, but not in such a large scale. This research studied the moods of 2000 people three times a day through software. This software asked the participants about their mood and what they were doing at these times. Their answers showed that unhappiness followed mind wandering, not the other way round.

But, some researchers feel that this theory needs more proof. They say that there is a link between bad mood and day dreaming. But, there is no sufficient proof to show the exact relationship between mood swing and daydreaming.

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

This study will help in the treatment of depression. People who suffer from a bout of depression can practice ways to check mind wandering. It can be done through yoga, meditation or keeping yourself busy. It is not humanly possible to completely cut down on day dreaming.

Though this study portrays the negative side of daydreaming, it is the fountain of creativity. So, it is not advisable to stop day dreaming altogether. The irony is that mind-wandering also underlies invention," says Smallwood. "We don't want to tell people not to do it." But, day dreaming can sometimes give us extra ordinary ideas.”