An Icelandic Family Study of Schizophrenia

At the present time there is a renewal of interest in the contribution of biological factors to schizophrenic illness. This stems in part from the success of pharmacological treatment and in part from the impressive findings in studies of foster-reared relatives of schizophrenics. While the pendulum of emphasis thus seems to be generally swinging in favour of constitutional influences, recent reports on twin studies have tended to go in the opposite direction. As will be discussed below, this development is largely attributable to a methodological error in the most recent twin investigations.