Happiness is contagious and spreads “in waves” among circles of friends or family members, but not including work colleagues, says a study published in the British Medical Journal.

Scientists have found that happy and unhappy people groups are formed by social and geographical proximity criteria. For example, the probability that a person be happy if 42% increase with a friend, who lives less than 800 feet away, gets himself happy.

This percentage drops to 25% if the friend lives less than 1.5 km and continue to decrease as the distance increases.

The odds of being happy increased by 8% for cohabitation with a life partner who is happy with 14% if a parent who is happy living nearby.

“Colleges do not affect the work of happiness, so the social context may limit the spread of emotional states,” the authors said.

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