A lot of people say that having high intelligence can be a double-edged sword. This can make any person rational and can do things easily. Yet, there are also some who are so intelligent that they cannot achieve satisfaction from the things that they do anymore. They sometimes feel that their lives do not have meaning. This can lead to their sadness and depression.
A high IQ may sometimes make a person feel fewer emotions as compared to other people. This might make them seem cold and heartless as compared to those who have normal or average IQ. Take note that having low intelligence has been correlated with depression. Basically, having low or high IQ can still be related to various mental illnesses and disorders.
Theoretically there should be no correlation between IQ and suffering from depression. The range of environmental stressors, loss of a loved one, war, disruption etc., can occur to anyone whereever they happen to score on an IQ test. However, a recent study of nearly 4,000 individuals in the top 2% of the distribution for intelligence, found that around a quarter suffered or had suffered from a mood disorder and 20% suffered or had suffered from an anxiety disorder. Both mood and anxiety disorders can include depression.
However, this sample was drawn from members of Mensa the "High IQ society" and it could be argued that people who opt to belong to such a society - indicating a preoccupation with their mental functioning and/or desire to demonstrate this with some social recognition - may be more prone to suffer from depression than those with high IQs who spend their time in sport, voluntary work or artistic endeavours. An earlier study of 50-year-olds found that those with high IQs in youth were less likely to be reporting problems with depression.