Individuals with psychotic illnesses are known to have a reduced fertility. It is unclear whether this is due to biological or social factors. Most fertility studies have been conducted in chronic schizophrenia, where confounders like medication and hospitalisation make this difficult to elicit. A less severe reduction of fertility has been observed in some ethnic minorities, but results are inconsistent.
We sought to investigate pre-morbid fertility in an ethnically diverse sample of individuals with first-onset psychosis. Data were derived from 515 people with a first psychotic episode (FEP) and 383 controls. We made case–control comparisons of differences in the proportion of those with children (fertility rates) and mean number of children (MNC). Analyses were then stratified by diagnosis, gender and ethnicity, and adjusted for potential confounders.
We found that FEP showed a reduced fertility rate (age-adjusted OR of having children 0.47 [95% CI = 0.39, 0.56]), irrespective of diagnosis, and there was little evidence of confounding by gender, ethnicity, religious background, education level, or history of past relationships (fully adjusted OR = 0.55, 95% CI = 0.37, 0.80). Women had a somewhat greater reduction in fertility rates than men (Men: age-adjusted OR 0.61 [95% CI 0.42, 0.89]; Women: age-adjusted OR 0.46 [95% CI 0.31, 0.69]) and we could not find any evidence of ethnic differences in the degree of fertility reduction. FEP who had previously experienced a stable relationship had an MNC that was comparable to that of the general population and had a later onset of illness.
This is the largest case–control study to date to investigate fertility in first-onset psychosis. Our data suggests that fertility is affected, even prior to the onset of a psychotic illness, and there are likely to be biological and environmental factors involved, but the former seem to have a stronger influence.
Individuals suffering from non-affective psychosis, particularly schizophrenia, have long been reported to have reduced fertility (Bundy et al., 2011) and this is most marked in men (Vogel, 1979, Nanko and Moridaira, 1993, Nimgaonkar et al., 1997, McGrath et al., 1999, Howard et al., 2002, Haukka et al., 2003, Webb et al., 2005 and Power et al., 2013). Not only are people with schizophrenia less likely to reproduce, but those that do have fewer offspring than healthy individuals (Nimgaonkar et al., 1997 and MacCabe et al., 2009). In the case of affective psychosis, there is weaker evidence of reduced fertility (Howard et al., 2002 and Murray et al., 2005), and some studies have found normal fertility (MacCabe et al., 2009).
With the exception of one small study looking at first episode psychosis (Hutchinson et al., 1999), previous research on fertility in psychoses has been carried out in people suffering from chronic psychosis. Therefore, it is very difficult to separate the impact of a predisposition to psychotic illnesses on fertility from the secondary effects of long-term hospitalisation, sexual dysfunction (Bobes et al., 2003), and neuroleptic-induced hyperprolactinaemia (Meaney and O'Keane, 2002).
We, therefore, sought to investigate pre-morbid fertility in a large, ethnically diverse sample of cases with a first episode of psychosis and population based controls drawn from the Aetiology and Ethnicity in Schizophrenia and Other Psychoses (AESOP) study (Morgan et al., 2006). In studying first episode cases at the point of illness onset, we hoped to reduce the impact of mediating effects mentioned above and capture data on pre-morbid fertility. We hypothesized that, as in previous studies, fertility would be reduced more significantly in people suffering from non-affective psychoses (Bundy et al., 2011) than in those with affective psychoses (MacCabe et al., 2009), and more in men than women (Vogel, 1979, Nanko and Moridaira, 1993, Nimgaonkar et al., 1997, McGrath et al., 1999, Howard et al., 2002, Haukka et al., 2003, Webb et al., 2005 and Power et al., 2013). We also aimed to conduct exploratory analyses comparing variation in the extent of reduced fertility between different ethnic groups, in order to test whether belonging to an ethnic minority conferred some protection against low fertility, as observed by others (Hutchinson et al., 1999 and Bhatia et al., 2004).
