Affective and non-affective psychoses show rural-urban variation

By Lucy Piper, Senior medwireNews Reporter

Rates of affective psychosis appear to be increased in more urbanised areas, study findings from France show.

The findings also confirm previous observations of increased rates of non-affective psychosis with urbanisation.

The researchers compared the rates of psychosis between an urban and rural catchment area, based on 2 years of data collected from the majority of practicing psychiatrists.

In the urban area, comprising seven towns with an overall population density of 7790/km², there were 96 cases of psychosis, giving a raw incidence of 36.02 per 100,000 person–years at risk.

This compared with 39 cases in a rural area of 164 towns with an overall population density of 71/km², equating to a raw incidence of 17.20 per 100,000 person–years.

Incidence rates of both affective and non-affective psychoses were increased in the urban area compared with the rural area, at 14.26 versus 5.73 per 100,000 person–years and 21.76 versus 11.45 per 100,000 person–years, respectively.

The researchers, led by Andrei Szöke (INSERM, Créteil), also note that rates of both were increased in the most urbanised populations of the rural area compared with the least urbanised and were close to those seen for the urban area.

They divided the population from the rural area into three groups, based on the size of the towns: the smallest towns (between 60 and 1350 inhabitants), medium towns (between 1350 and 4650 inhabitants) and largest towns (between 4650 and 19,124 inhabitants).

The raw incidence rates for affective psychosis were 2.64 per 100,000 person–years in the smallest towns, compared with 9.51 per 100,000 person–years in the largest towns. The rates for non-affective psychosis were 1.32 versus 23.09 per 100,000 person–years.

“Our results suggest that, even in a globally rural area, incidence is still influenced by the size of a city”, the team writes in BMC Psychiatry.

Non-affective psychosis tended to be more frequent in men than women and in those aged 18–24 years, compared with individuals aged 55–64 years. And these differences were more pronounced in the rural area than the urban area.

By contrast, affective psychosis was slightly more common in women than men and there was less variation with age.

Szöke et al say that “[u]rbanicity is probably a proxy for some underlying, as yet unidentified, risk factor.”

Licensed from medwireNews with permission from Springer Healthcare Ltd. ©Springer Healthcare Ltd. All rights reserved. Neither of these parties endorse or recommend any commercial products, services, or equipment.