Increase in harm avoidance by genetic loading of schizophrenia

Schizophrenia is highly familial neuropsychiatric disorder with heritability estimated at 60% to 90%. Even unaffected first-degree relatives of schizophrenia manifested some neuropsychologic abnormalities, neurologic soft sign, and morphologic anomalies. Because personality traits are under genetic influence and considerable heritability, we intended to evaluate temperament and character of first-degree relatives of schizophrenia and the influence of schizophrenia genetic loading on their temperament and character.

Temperament and Character Inventory was completed by 97 first-degree relatives of schizophrenia or schizoaffective disorder, 48 schizophrenic probands (44 patients with schizophrenia and 4 patients with schizoaffective disorder), and 106 control subjects. Within first-degree relatives, parents who have additional probands with schizophrenia spectrum disorder in their ascendant or collateral pedigree and siblings who have offspring with schizophrenia spectrum disorder were defined as presumed carriers (n = 20). Group differences in Temperament and Character Inventory scores were compared using a mixed-model analysis of variance with family as a random effect and age as a covariate.

Harm avoidance (HA) scores increased in the order of control subjects, the first-degree relatives, and probands. Among the relatives, presumed carriers, but not presumed noncarriers, had higher HA compared with control subjects. In addition, probands showed significantly low reward dependence, low self-directedness, and low cooperativeness scores compared with the first-degree relatives and control subjects. Probands had also higher self-transcendence scores than the first-degree relatives and had lower persistence scores than control subjects.

Our findings that HA increases in proportion to the genetic loading of schizophrenia suggest that it may be a potential endophenotype of schizophrenia.