It's a fine line separating intelligence and insanity. According to a new study, the same gene that makes you smarter also makes you more likely to go crazy:

Most people inherit a version of a gene that optimizes their brain's thinking circuitry, yet also appears to increase risk for schizophrenia, a severe mental illness marked by impaired thinking, scientists at the National Institutes of Health's (NIH) National Institute of Mental Health (NIMH) have discovered. The seeming paradox emerged from the first study to explore the effects of variation in the human gene for a brain master switch, DARPP-32. The researchers identified a common version of the gene and showed how it impacts the way two key brain regions exchange information, affecting a range of functions from general intelligence to attention. Three fourths of subjects studied had at least one copy of the version that results in more efficient filtering of information processed by the brain's executive hub, the prefrontal cortex. However, the same version was also more prevalent among people who developed schizophrenia, a severe mental illness marked by delusions, hallucinations and impaired emotion that affects one percent of the population.

This actually makes sense. The human brain is a pattern-making machine. We imagine causality and see intentionality everywhere. Schizophrenics suffer from an excess of patterns.* (A delusion is just the perception of a pattern that doesn't actually exist.) So it's entirely plausible that the same gene that endows with us the machinery to detect patterns (this involves the prefrontal cortex) is also involved with the machinery underlying madness. As G.K. Chesterton once said, "The madman is not the man who has lost his reason. The madman is the man who has lost everything except his reason."

*The firing rates of dopamine neurons are largely responsible for our pattern detection abilities, at least when it comes to rewarding stimuli. Dopamine has also been implicated in many of the symptoms of schizophrenia, which seem to be partially caused by an excess of certain dopamine receptor subtypes.