BackgroundAlthough schizotypal traits, such as anhedonia and aberrant perceptions, may increase the risk for schizophrenia-spectrum disorders, little is known about early-life characteristics that predict more pronounced schizotypal traits.AimsTo examine whether birth size or several other early-life factors that have been previously linked with schizophrenia predict schizotypal traits in adulthood.MethodParticipants of the Northern Finland 1966 Birth Cohort Study (n= 4976) completed a questionnaire on positive and negative schizotypal traits at the age of 31 years.ResultsLower placental weight, lower birth weight and smaller head circumference at 12 months predicted elevated positive schizotypal traits in women after adjusting for several confounders (P<0.02). Moreover, higher gestational age, lower childhood family socioeconomic status, undesirability of pregnancy, winter/autumn birth, higher birth order and maternal smoking during pregnancy predicted some augmented schizotypal traits in women, some in men and some in both genders.ConclusionsThe results point to similarities in the aetiology of schitzotypal traits and schizophrenia-spectrum disorders.