Researchers from the University College London in a study of 6,870 people found that low intelligence was often linked with lower income and poor mental health, which contributed to unhappiness, the BBC News reported.
The team analysed data from the Adult Psychiatric Morbity Survey in England.
One of the questions was: "Taking all things together, how would you say you were these days - very happy, fairly happy or not too happy?" People's verbal Intelligence quotient (IQ) was also assessed.
The highest proportion saying they were "very happy" was found in people with an IQ between 120 and 129 - 43 per cent said they were very happy.
The highest proportion saying "not too happy" - 12 per cent - was found in people with an IQ between 70 and 79.
"The study suggests that higher IQ appears to be associated with improved wellbeing, but that this relationship between IQ and wellbeing is partly due to higher IQ being linked with better income, health and less mental illness," Dr Jonathan Campion, a consultant psychiatrist and director of public mental health at the South London and Maudsley NHS Foundation Trust, said.
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He added that the study was helpful in identifying some of the factors that mediate the association between IQ and happiness, as well as highlighting interventions to prevent lower IQ leading to greater unhappiness.
The study was published in the journal Psychological Medicine.