Risk Factors Schizophrenia

The Effect of Perinatal Risk Factors on the Incidence of Schizophrenia


Developing schizophrenia is dependent on different factors. A person who could possibly develop the illness later in life is faintly unusual in terms of cognitive skills, motor functioning, and social behavior as compared to his or her peers. This states that indicators exist as to whether a person will be vulnerable into being a schizophrenic later in life, as dictated by certain abnormalities that can be observed (Mortensen, 1999 and Dean, 2003).

Most of the causes being held accountable for the development of schizophrenia can be traced back to genetic or biological factors and environmental exposure that operated early in life of the individual (Dean, 2003, Khasshan, 2008, Mednick, 1970, and Mortenen, 1999).

Evidences regarding the effects of obstetric complications, prenatal illness, misuse of drugs, migration and travel, urbanization, and various life experiences on the onset of schizophrenia in later years in life have been noted. These were even incorporated and represented in causation models that encompass psychological, genetic, environmental, and social elements. These evidences can be used as models for clinical and research purposes of determining the risk of schizophrenia, as they cover a wide range of causative agents (Dalman, 1999 and Dean, 2003).

It has been a challenge for researchers to understand the cause of schizophrenia, the etiology of which has brought about several hypotheses (Dean, 2003). Different risk factors affect the incidence of the illness, two of which will be given more attention in this paper. A number of epidemiological studies have indicated an increased risk of developing schizophrenia among people who were exposed to maternal infections such as rubella virus and influenza virus in utero (Westergaard, 1999). Other studies have shown that children who were born during inclement weather have an increased risk of developing schizophrenia. These are supported by researches conducted on a population basis (Mortensen, 1999).


As stated by the study conducted by Mortensen and others (1999), the location and the season of birth of an individual might be important in the development of schizophrenia. Aside from family history, these environmental factors can be associated with the onset of the disorder. Prevalence studies of Westergaard and others (1999) also showed that exposure to prenatal infections might be a factor in the development of schizophrenia later in life. There is, however, a poor evidence of a strong association between development of schizophrenia and exposure to influenza viral infection. This lead the group into determining whether or not prenatal exposure to rubella would indeed be a factor for schizophrenia development. This is in accordance with previous researches that rubella viral infection might be a significant cause for the illness. With all these research supports as foundation for a prospective study, this paper aims to give a sound explanation on how certain factors might affect the possible development of schizophrenia later in life. This study will focus on two possible causative agents as parameters.

The main purpose of this study is to determine if being born in severe weather, such as extreme hot or cold temperatures, or being exposed to the rubella virus in utero is linked to developing schizophrenia later in life.

Research Hypothesis

We hypothesized that there would be an increase in the incidence of early adult onset schizophrenia among those exposed to the rubella virus in utero and those born in winter months.

Literature Review

Several studies have been conducted on risk factors for schizophrenia. One study examined the outcome in 70 individuals whose mothers had rubella infections during pregnancy. Rubella is known to cause severe developmental problems in exposed fetuses. These individuals’ risk of having schizophrenia by the time they reached the mean age of 22 years was five times higher than normal

It has been proposed that environmental factors may also be important in determining risk for schizophrenia. A study done by Mortensen and others (1999) showed that the place and season of birth account for many more cases of schizophrenia than family history of the disease, and family history has been the best-established risk factor. The group’s study found out that the risk for schizophrenia was highest for births in February and March and lowest for births in August and September. Another study conducted by Mortensen and others (1999) concluded that schizophrenia was positively associated with birth in late winter.

On the other hand, Hultman and others (1999) emphasized the evidences shown by neuropathological researches that the aberrations caused by pathogen invasion disrupt proper brain development. This in turn contributes to the onset of schizophrenia that might even be developed earlier in life than expected. This proposed hypothesis can be associated with the link between obstetric complications and schizophrenia, as both are dependent on risks brought about by prenatal infections, which in turn are connected with neurodevelopment of an individual.

Theoretical Framework

The physiological framework of this study is based on the notion that conditions during pregnancy have an effect on the fetus’ psychological development, specifically, the impact of season of birth and exposure to the rubella virus.

The prenatal conditions of an individual have a direct effect on the person’s future genetic and phenotypic make-up. The most important contribution of the obstetric development lies on the possible alterations on the genes of the individual. Exposure to such abnormalities has a considerable intervention with the normal functioning of the brain (Khasshan, 2008). This means that exposure to infections such as rubella virus has a meaningful link to schizophrenia development of the individual exposed to the pathogen in its prenatal stage.

This is serves as one of the backbones of this study, as it is the foundational basis whether the link between congenital exposure to rubella and schizophrenia onset has reliable evidence.

After the study which dwells more on the biological or genetic factors, the study will consider the environmental elements that can also be potential risk factors for the disorder. It has been established that the over-all make-up of an individual lies on genetic and environmental factors. The second part or backbone of the study concerns the environmental exposure effects as dictated by season of birth. This can be of importance since extreme weathers might affect a mother psychologically and physically, thereby creating an impact on the life inside her womb. Being born on extreme hot and cold weather can hence be linked to the development of schizophrenia later in life of an individual (Mortensen and others, 1999).

Significance and Need for the Study

The proposed study is important due to the health and psychological concerns of schizophrenia. Being a disorder which affects the entire lifestyle of the affected individual, it is of great significance to research about the etiology of the disease (Dean, 2003).

Prenatal exposure to rubella viral infection might be a cause of the onset of schizophrenia, as well as the environmental effect of being born on an extreme season. Knowledge on these prenatal risk factors can contribute additional information on how to prevent schizophrenia development in an individual.


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