Possible reasons are
- Overthinking and over evaluation
- Easy access to wide variety of options
- Over critical and too wider imagination
Intelligence has a weak loophole. It presents you with too many options. Intelligent people are known to worry more than required as they are able to think of a bigger spectrum of thoughts. They need constant reassurance else their mind makes their life quite boggle some.
Who gets bored more often, smart people or dumb ones?