Is there an increase of reproductive rates in schizophrenics?

Abstract

It is well-known that the fertility of schizophrenic patients, particularly males, is below the population average. The main measures of fertility (reproductivity) are marriage rate, marital fertility, and rate of reproduction. A review of the literature reveals the rate of reproduction of schizophrenic patients to be 30% to 80% of the general population, the reduction being mainly due to reduced probability of marriage. At least one investigation presented evidence for an increase in marriage rate and rate of reproduction in schizophrenic patients relative to the general population in recent time. If this increase were to be confirmed it would undoubtedly have practical as well as theoretical implications. The hypothesis of a compensatory higher fertility of healthy relatives of schizophrenics based on a physiological advantage is empirically unproven. Additionally, the concept of a balanced polymorphism in schizophrenia rests on a superficial analogy with Mendelian traits.

Reproductive fitness in familial schizophrenia

“…This model predicts that in familial forms of schizophrenia, in which maximal effects of selection are likely, empirical evidence for reduced reproductive fitness should be found. Although there is strong evidence for decreased reproductive fitness in unselected samples of schizophrenia (Haverkamp et al, 1982), surprisingly fitness has not previously been examined in familial schizophrenia. A finding of reduced fitness in familial schizophrenia would be of particular interest given a recent finding of anticipation (worsening severity and decreased age at onset across generations) (Bassett and Honer, 1994).…”

“…This theory has generally not been supported by studies of siblings of schizophrenic subjects (Erlenmeyer-Kimling, 1978;Gottesman and Shields, 1982;Haverkamp et al, 1982). Relatively few studies have been done, however and none has assessed siblings for diagnoses such as schizophrenia spectrum conditions that are most likely to be associated with gene carrier status.…”

“…Many older studies of reproductive fitness had methodological flaws involving the assessment of fitness and the comparison to norms (Haverkamp et al, 1982). Some studies report only 'marital fertility', the number of offspring of married individuals (Haverkamp et al, 1982;Lane et al, 1995).…”

“…Some studies report only 'marital fertility', the number of offspring of married individuals (Haverkamp et al, 1982;Lane et al, 1995). Reproductive fitness of all individuals regardless of marital status is the only measure relevant to genetics and the issue of selection (ErlenmeyerKimling et al, 1980).…”

“…Reproductive fitness of all individuals regardless of marital status is the only measure relevant to genetics and the issue of selection (ErlenmeyerKimling et al, 1980). In addition, few studies of schizophrenia have used norms that controlled for the age of the sample (Haverkamp et al, 1982) and some have used small control samples which can introduce errors (Reed, 1959).…”