A psychiatric-psychological study of XYY males found in a general male population.

The psychological test results of five XYY males from in a population study showed an intellectual level within the normal range but with a mean full scale IQ and educational level lower than expected. The cognitive as well as emotional function was characterized by immaturity, manifested in passivity, unreflectiveness and emotional liability, in three resulting in uncontrolled aggressive outbursts. Conflict material also appeared immaturely resolved, centering around unfulfilled needs of contact and insecure masculine identification. The defense mechanisms used were generally rather weak, but only in one subject did the anxiety level seem to be excessively low. All five males differed to a certain extent from their siblings; three of them were hyperactive, restless, hot-tempered and impulsive at school and four of them had difficulties at school. Three learned a trade, but only one stayed in his trade, and one was applying for disablement pension on account of personality deviation. Two of the five had a criminal record. It is concluded that the presence and degree of the above-mentioned characteristics of XYY males varied. It is evident that environmental factors play as great a role for the development of personality and behaviour in males with karyotype 47, XYY as in males with a normal chromosome constitution.