Hand preference in psychotic twins

Area of Science:

• Neuroscience
• Psychiatry
• Behavioral Genetics

Background:

• Hand preference, specifically left-handedness, has been an area of interest in relation to functional psychosis.
• Previous research suggested a potential link between non-right-handedness and psychosis, particularly in monozygotic twins.

Purpose of the Study:

• To replicate a seminal study on hand preference in twins with functional psychosis.
• To investigate whether left-handedness is more prevalent in monozygotic versus dizygotic twins with psychosis.
• To examine the relationship between within-pair left-handedness and psychosis discordance in twin pairs.

Main Methods:

• Examined hand preference for writing in 30 monozygotic (MZ) and 30 dizygotic (DZ) twin pairs.
• Probands in these twin pairs had a history of functional psychosis.
• Compared rates of left-handedness between MZ and DZ twins, and between psychotic and nonpsychotic individuals.

Main Results:

• No increased rate of left-handedness was observed in MZ twins compared to DZ twins.
• No higher prevalence of left-handedness was found in psychotic twins relative to nonpsychotic twins.
• No association was identified between within-pair left-handedness and discordance for psychosis.

Conclusions:

• The findings contradict previous reports suggesting a link between left-handedness and psychosis in twins.
• The study did not find evidence supporting an association between non-right-handedness and psychosis or its discordance in twin pairs.
• Reasons for the discrepancy with prior research are discussed, highlighting the need for further investigation into the etiology of psychosis and handedness.