Young men are more likely to experience first-episode psychosis, defined as the first manifestation of one or more severe mental disorders including schizophrenia, bipolar affective disorder, and depression, compared to women of the same age group, says a new study. The findings published in the journal JAMA Psychiatry also showed that ethnic minorities and people living in socioeconomically disadvantaged areas are also vulnerable to severe mental illness. For the study, the researchers estimated the incidence of first-episode psychosis in six countries -- England, France, Italy, the Netherlands, Spain and Brazil. "The study confirmed that the incidence of first-episode psychosis varies considerably between major cities and rural areas. It also showed that environmental factors probably play a crucial role in this significant variation," said one of the researchers Paulo Rossi Menezes, Professor at University of Sao Paulo Medical School (FM-USP) in Brazil. "Until the end of the twentieth century, the etiology of psychotic disorders was believed to be mainly genetic, but the results of this study show that environmental factors are extremely important," Menezes said. The study showed that the incidence of first-episode psychosis was higher among men aged 18 to 24 than among women in the same age group. Menezes said this finding confirms fairly consistent data in the literature. He noted that the incidence of first-episode psychosis among young adult males is higher than among young adult females according to previous research, which also shows that as men approach 35, it tends to converge with the incidence among women. In women aged 45-54, it is slightly higher than among men in the same age group. "We don't know exactly why there are these differences in incidence between sexes and age groups, but they may be linked to the process of cerebral maturation: the brain matures between the ages of 20 and 25, and during this period, men seem to be more vulnerable to mental disorders than women," Menezes said. The researchers also found that the incidence of first-episode psychosis is high among ethnic minorities and in areas with less owner-occupied housing.