Schizophrenia Daily News Blog

Social Factors in the Development of Schizophrenia: A Review of Recent Findings

In this entry we've summarized a recent journal article that reviewed the results of 84 different research studies done over the past 20 years on social and environmental causal factors that have been identified in schizophrenia.

Our summary sheds light on possible approaches to prevention of schizophrenia, and also of treatment. Although a great deal of research effort goes into schizophrenia genetics and medications, this article describes research that suggests that modifying social and environmental factors are likely an equally important pathway to prevention. In fact today the area of neuroscience research related to schizophrenia genes, biology and social factors are increasingly seen as overlapping and interdependent domains. This new area of research that focuses on the intersection between social factors and neuroscience has only developed in the past 5 years and is called social neuroscience. One important area of focus of social neuroscience is the way in which stressful situations can impact brain development.

Altering the environment (at the family, or neighborhood level) may be much more achievable than genetic or drug-based risk modification strategies, because everyone can begin making some changes immediately, and the therapies are not limited to approaches that must be provided by researchers in a lab. For people with a strong science background, a link to the full journal article is provided at the end of this summary.

Its important to understand that brain research has now shown that the social and emotional environment that a person experiences prior to birth, and during childhood has a long term impact on brain development, right down to the level of cells and genes. If you want to learn more about this new area of research where social factors intersect with biology - read this story: Social Intelligence and also this story and this story.

Who did the study?

This study was conducted by Elizabeth Cantor-Graae, PhD, and was supported by grants from the Stanley Medical Research Institute and the Medical Council of Sweden. It is released in the May issue of the Canadian Journal of Psychiatry.

Why did they do it?

The goal of this research was to examine the social factors that have been identified as likely contributors in people developing schizophrenia. Much of the research today is devoted to understanding the biology and the genetics of schizophrenia, while less focus is on environmental and social factors (even though a large body of research supports the interaction of genetics and environment as determinants for the illness). Some people argue that understanding environmental and social factors can be even more helpful than genetics because it’s easier to manipulate these external factors. This review article also looked at research process issues and possible ways to improve future research efforts.

"The purpose of this review is to critically examine recent evidence suggesting that social factors contribute to etiology [causes] of schizophrenia and to highlight possible methodological issues and problems that need to be resolved."

How did they do it?

This study is what some researchers refer to as a meta-analysis, which is a study of many different research articles on the same subject. This is often a great way to paint a bigger picture of the issue, in this case, social factors and schizophrenia. The researchers conducted reviews of studies done on social factors and schizophrenia using MEDLINE. All the studies reviewed were completed after 1996, and were in English journals. The studies were either peer-reviewed or review articles that included DSM diagnostic criteria for schizophrenia, as well as standardized assessments of psychosis. This means that only studies that used reliable and valid assessments of the disorder and its symptoms were included in the review. The article includes 84 references, which provide a broad overview of the research on social factors and schizophrenia.

Who were the participants?

Because this is a review of many different studies, and even a review of several reviews, many different populations were participants. Most studies focused on migrants in Europe, UK, and Australia, as well as animal research.

What results did this review find?

Migrant Studies: In migrant studies dating from 1977-2003, they found much higher relative risk for developing schizophrenia in several groups (study on immigration stress as a high risk factor). They found that not only did 1st generation immigrants have a higher risk of schizophrenia then the general population (including the population of the immigrants “home” country) but the 2nd generation immigrants had the highest risk rate. They also found immigrants from countries were most people had skin color that was “black” had a very high-risk rate.

The review outlines several discounted hypotheses that attempted to explain the migrant risk increase; these ranged from viruses, genetics, and vitamin D deficiency during pregnancy. But the author of this study argues that, “social causation is the most likely unifying hypothesis for findings of increased schizophrenia risk in immigrant groups” especially those with such ranges in ethnicity, as well as findings that point to a greater risk in 2nd generation immigrants. Long term exposures to social defeat or chronic experiences of discrimination are the underlying factors.

The Social Defeat Hypothesis: The social defeat hypothesis integrates both social and biological factors that contribute to the development of psychotic symptoms, which allows it to be show the relationship between the environment (social defeat) and the biology (what happens internally when exposed to the social defeat or discrimination). Social defeat is commonly defined as a subordinate position or as ‘outsider status’. Some ways that people may be exposed to social defeat is believed to be through longer term social environment situations (or isolation) that a person interprets as being negative and due to racism, social economic status, gender, sexual orientation, language barriers, or prejudice.

"According to this model, long term experiences of social defeat lead to sensitization of the... dopamine system and (or) to increased baseline activity of this system, thereby, to an increased risk for schizophrenia."

Animal Studies: Most of the research supporting this model has been done with animals. Monkey studies show that social subordination and social isolation cause hyperactivity of this dopamine system. Schizophrenia research has found that dopamine plays a role in psychosis and that’s how most anti-psychotic drugs do their work. Anti-psychotic drugs decrease dopamine activity, particularly on the D2 receptor.

In rats, social defeat stress shows increased dopamine activity in the specific areas of the brain that have been linked to schizophrenia. But following the social defeat stressor with social isolation induced greater dopamine changes, while following it with a familiar social environment prevented the adverse consequences.

In both animals studies they showed increased vulnerability to the reinforcing properties of cocaine, and were more sensitive to dopamine agonist drugs. This is similar to how people with schizophrenia fair with dopamine agonist drugs; they have increased sensitivity to the drug’s effects.

Human Studies: Human studies have found correlations between being discriminated against and developing psychotic symptoms (in people who were healthy prior to the exposure to the discrimination). Other research has shown that those immigrants with “black” for darker skin color (in a country inhabited predominantly with "white" or lighter skin people) or those coming from a developing country were at a higher risk. The author speculates that these immigrants received the greatest discrimination and social defeat in the new country; therefore increasing their risk for schizophrenia.

On the contrary, others have attributed the increased risk in these groups to their “low social economic status, lower educational achievement, higher rates of unemployment, and poorer housing conditions.” But the author emphasizes that there must be an explanation of the underlying biological mechanisms in those factors that contribute to a brain disorder. Meaning that right now, at least, researchers don't yet understand how the social factors precisely impact the biological processes that lead to schizophrenia.

It's also suggested that social defeat may be the common denominator in the other factors proposed. Poor education, low social economic status, and unemployment have all been correlated with social exclusion, therefore being part of social defeat.

Social Inequality, Social Adversity & Family Upbringing: Many studies point to the connection between social factors at birth and during childhood that may increase risk for developing schizophrenia. Some of the researchers argue that these social factors are not independent of mental illness of the parents or the family system. This means that the mental illness in the family is perhaps the cause of the debilitating social factors contributing to schizophrenia. For example a parent with schizophrenia may not form secure attachments with their child, or a parent with bipolar disorder, or depression, or anxiety may not be able to provide a positive and stable environment for the child to grown up in. Parental mental illness has been found to greatly increase risk of mental illness in the children, but research that looked at social factors still found an increased risk for schizophrenia after controlling for parental mental illness. Controlling for a factor means that the study could not attribute the increased risk to that factor, in this case parental mental illness.

"Whatever the nature of the risk factors involved, environmental factors play a significant role in the etiology (causes) of schizophrenia."

Other review studies focusing on multigenerational immigrant households found social adversity explained much of the adults elevated risk for schizophrenia, but only explained little of the risk in children and adolescence. Social adversity was defined as illness, social drift, and other social economic factors. Youths may have been impacted to a lesser extent, by such factors, especially social drift (social drift is often referred to as impairment in functioning, due to any form of illness, mental or physical, that can result in the drift down the social scale).

Cannabis and Drug Use: It has been suggested that drug use, specifically cannabis may be a cause of the immigrant increased risk. But often times there are no differences in cannabis use rates between immigrants and natives, and the cannabis research shows a gender difference (males use more, or are more likely to use) that is not seen in the migrant risk for schizophrenia. The author of this review encourages more research into the role drugs play in social factors causing schizophrenia.

Stress and Social Adversity: Social adversity may lead to stress, and stress is a factor related to onset, severity, and expression of schizophrenia. This means that stress exacerbates schizophrenia symptoms, and may increase psychotic episodes. But research also shows that stress is likely a casual factor for the development of schizophrenia.

The author suggests that stress related to social rank or social economic status may be exceptionally harmful. A lot of research (both animal and human) has shown that low social and economic status (SES) or low social rank correlates with poorer health, and increases in physiological problems. This has been attributed to many things, lack of access to health care and resources, stress related to money or discrimination, and even decreased self-esteem. But that is not to say that poverty or low SES causes these things. How these individuals interpret their situation may be more important than the situation itself. This means that someone who bases their value on their social situation, what others think of them, or their monetary value, would react very negatively to low social and economic status or discrimination. This suggests that how people interpret their life can be a protective factor, or a risk factor. (read more here about the importance and value of a growth mindset, and of teaching children a positive outlook on life as covered in positive psychology )

Stressors seen in children show up as risk factors for schizophrenia; some of these stressors include, single-parent homes, long periods of separation from either parent, parental loss, parental unemployment, and households receiving welfare or poverty (study on social adversity in children).

Childhood Abuse and Family Dysfunction: Child Abuse is a hot topic in schizophrenia research today, and opinions are polarized. Some claim abuse is THE cause for schizophrenia, while others say it may be one of many causes, and a select few have done studies finding no correlation between the two. The author points out an interesting interpretation of these polarized beliefs; "childhood abuse may be a marker for other potential relevant risk factors, such as family dysfunction."

Family dysfunction has been linked to increased schizophrenia risk in those with genetic vulnerability. The Finnish adoption study found an 86% decrease incidence of developing schizophrenia in people with high-genetic risk for schizophrenia-spectrum disorders when placed in a healthy family environment. This supports the idea that abuse may be just a portion of what causes schizophrenia, and family dysfunction seems to include many aspects of associated risk factors.

A study on children and adolescents in The Netherlands found that family dysfunction was a separate factor in the immigrant’s increased risk. The immigrant children and adolescents had a greater risk for schizophrenia from the general population, but those that were in families with signs of dysfunction had an even greater risk. This review also touches on the smaller pool of research that shows family cohesion and social networks, thought to be opposite of dysfunction, to be protective factors in the development of schizophrenia.

Neighborhood: Differences were noticed in the risk for schizophrenia associated with neighborhood features. In neighborhoods with minorities (non white) that were at an increased risk, researchers have found that the risk went down when the neighborhood population increased with other minorities. Its been speculated that this decrease in risk is associated with an environment of less discrimination, and more support or familiarity. Opposite results were found with single and (or) divorced people at risk. If these single or divorced individuals lived in neighborhoods that were predominantly made up of others that were single or divorced, the risk went up. This might be attributed to the isolating properties of being single, and the environment encouraged it further.

These studies are not large enough or diverse enough to say that living in a neighborhood that’s full of people similar to you (if you are a minority) or different from you (if you are single or divorced) is a good way to decrease risk. But they do point out that there are some social factors contributing to the differences, even down to neighborhood dynamics.

Urban Effect: There is a large body of research out that shows in most areas, children born in urban environments are at an increased risk for schizophrenia. Research has even seen a dose-response effect for the urban effect. That means that the more urban the environment (dose), the more risk for developing schizophrenia (response).

A 2005 review of the urban effect found “the rate of schizophrenia in urban areas is about twice that in rural areas”. Some studies defined urban cities as the number of people relative to area surface; others, as number of addresses relative to area surface; and yet others, as large city versus small city based on absolute population counts.

The urban effect is not consistent among all countries; some Australian research has no increase in psychosis among urban areas.

Currently, there is no solid explanation for the urban effect. Researchers have all found a variety of factors that may contribute to this increased risk; such as, environmental pollutants, crowding and illness, social adversity, stress, and other biological causes. More research into whether social factors are contributing to the urban effect needs to be done.

What are the conclusions?

The review clearly states there is no evidence that schizophrenia is entirely caused by only genetic or only social factors, and that an intricate interplay of genetic/biology and social/environmental factors are the culprit. But because much of the evidence for social factors has shown a dose-response effect, which means that the more of the social factor present (dose), the greater the risk for schizophrenia (response), its clear that social causality has some validity.

"Factors, operating on the societal, neighborhood, and family-individual level contribute to enduring liabilities that may lead to manifest schizophrenia."

Researching these social causes is a difficult process. Because social defeat, discrimination, stress, and low social economic status are unpleasant and possibly dangerous, research cannot expose people to such factors and then measure the outcome. Many extraneous variables (things that may interfere with results) come up in psychology research that focuses on environmental factors.

Another difficulty is that depending on genetic risk factors, these social factors can cause a variety of mental illnesses. This is an integrative theory (much like the biopsychosocial model) that says people are vulnerable to many things based on genetics and biology, but that external (both environmental and social) factors work in concert to “bring out” or "expose" these vulnerabilities. Within that idea is the notion that every persons biology and vulnerability is different. So, for example, social isolation may bring out schizophrenia in one individual, but the same social isolation could bring out depression in another person who has different genes and biology.

More research on social factors needs to be conducted. Until then, it’s clear that social factors are influencing those at risk for schizophrenia; the precise biological means by which this takes place is still being researched. As stated earlier, the importance of understanding the social causal factors involved in development of schizophrenia is that they offer significant potential in the area of prevention and treatment of schizophrenia. Altering the social and environment is likely to be a much easier,faster and more cost-effective task than trying to change people's genetics or biology.

This review shows that within every system of society, countries, ethnicities and cultures, cities, neighborhoods, as well as the smallest system, families, there is an opportunity to decrease risk for schizophrenia. Community programs decreasing discrimination, increasing general social and economic status, and improving support networks are of great benefit to the mental health of that community. Additionally, Therapy that incorporates the family as well as the individual’s mental illness is also of great benefit to the recovery process, and also potentially in preventing schizophrenia, in situations where it improves how a family functions.

PDF of full article:
The Contribution of Social Factors to the Development of Schizophrenia: A Review of Recent Findings.

This review was motivated by this short article on social defeat:
Social defeat: risk factor for schizophrenia?

Related Reading: Prevention Tactics for Schizophrenia