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26-10-2010 | Mental health | Article

Research confirms reduced fertility in schizophrenia patients


Free abstract

MedWire News: Results from a systematic review and meta-analysis confirm that individuals with schizophrenia have reduced fertility compared with the general population.

Furthermore, the researchers found that unaffected relatives of schizophrenia patients do not have higher fertility rates than the general population, suggesting no "compensatory fitness advantage" in unaffected relatives to explain maintenance of schizophrenia in the population.

"There is now strong evidence, from numerous studies, that patients with schizophrenia, particularly men, have reduced fertility (number of offspring) compared with the general population," explain James MacCabe (King's College London, UK) and colleagues.

They add: "This gives rise to what has been termed the 'schizophrenia paradox': how are genetic variants predisposing to schizophrenia maintained in the population, in the face of the markedly reduced biological fitness of patients with schizophrenia."

To assess fertility rates in schizophrenia patients, and to investigate the hypothesis that increased fertility in unaffected relatives explains the 'schizophrenia paradox', the researchers searched the literature for relevant studies.

In total, six studies involving more than 1,070,000 schizophrenia patients, their unaffected relatives, and mentally healthy individuals were included in the final review.

Analysis of the pooled data revealed that patients with schizophrenia had significantly reduced fertility compared with the general population, at a fertility ratio (FR) of 0.39.The unaffected siblings of patients with schizophrenia had slightly lower fertility compared with the general population, at a FR of 0.96.

There was no significant difference in fertility between the parents of schizophrenia patients and the general population, although there was a trend toward increased fertility in the former group, at a FR of 1.17.

Among schizophrenia patients and their mentally healthy siblings, men had reduced fertility compared with women, at FRs of 0.54 and 0.81, respectively.

MacCabe and team conclude in the journal Acta Psychiatrica Scandinavica: "We have confirmed the finding that patients with schizophrenia have reduced fertility compared with the general population, with this reduction being more severe in men than in women.

"We have also demonstrated that there is no significant increase in the fertility of siblings or parents of patients with schizophrenia and the general population."

They add: "This suggests that there is no compensatory fitness advantage in siblings or parents of patients with schizophrenia."

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Mark Cowen

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