Aetiology of Mental Disorders

 Aetiology of Mental Disorders

When the lay public is asked to prioritize their causal beliefs for a vignette depicting either schizophrenia or depression, psychosocial causes are most popular for depression, but a large proportion of respondents prefer biological causes for schizophrenia. It therefore follows that knowing about the lay public's causal beliefs about mental diseases before knowing about the scientist’s, is a prerequisite for providing adequate information and education to both patients and the public. Jorm's review on mental health literacy (2000) stated that the public for instance regards depression and schizophrenia most often to be caused by the social environment, particularly recent stressors. A review of population studies concluded that while this holds true for both depression and schizophrenia when using an unlabeled case vignette as a stimulus (e.g. Lauber et al., 2003; Magliano et al., 2004), the picture is unclear in studies explicitly referring to the diagnosis of schizophrenia.

 What Really Causes Mental Disorders?

Mental disorder is complex and as such, it is difficult to state what the causes are. The influences that potentially contribute to mental disorder are numerous, and competing theoretical models have disputed the emphasis to be given to individual and social influences, nature versus nurture, and biological or psychological factors. What is most important to reiterate is that the causes of health and disease are generally viewed as a product of the interplay or interaction between biological, psychological, and sociocultural factors. This is true for all health and illness, including mental health and mental disorder. For instance, diabetes and schizophrenia alike are viewed as the result of interactions between biological, psychological, and sociocultural influences. With these disorders, a biological predisposition is necessary but not sufficient to explain their occurrence (Barondes, 1993). For other disorders, a psychological or sociocultural cause may be necessary, but again not sufficient.

There are however some practitioners that have spoken boldly about the biological model leaving other models.  As a comprehensive model of the causes and effects of mental disorder and its treatment, the bio-medical tradition has been found increasingly wanting. Sociologically-based explanatory models have been advanced which have gone beyond the quite strict confines of disease detection and looked to personal and cultural reactions to disease for a greater understanding of mental disorder. Epidemiologists and public health professionals have stressed the significance of deprivation, poor housing and unemployment as causal factors. Whatever the make-up, the complexity and multiplicity of potential causal factors sets the mental health practitioner to approach aetiology of mental disorders cautiously. However experts generally say that mental disorders are caused by several factors and that in most instances the causes interact. Below we list some of the notable ones.

 

 Genetics (heredity) and The Environment

Many mental disorders tend to run in families, suggesting that people who have a family member with a mental disorder are more likely to develop a mental disorder. Mental disorders do occur in people who have a first-degree relative with the disorder, such as a parent, brother, or sister. People who have second-degree relatives (aunts, uncles, grandparents, or cousins) with the disease may also develop mental disorder more often than the general population. The risk is highest for an identical twin of a person with mental disorder. He or she has a 40 to 65 percent chance of developing the disorder.

Susceptibility is passed on in families through genes. Experts believe many mental disorders are linked to abnormalities in many genes and not just one. That is why a person inherits a susceptibility to a mental disorder and doesn't necessarily develop the illness. Mental disorder itself occurs from the interaction of multiple genes and other factors such as stress, abuse, or a traumatic event like death of a loved one which can influence, or trigger, an illness in a person who has an inherited susceptibility to it.

Studies suggest that mental disorder may result in part when a certain gene that is a key to making important brain chemicals malfunctions. This problem may affect the part of the brain involved in developing higher functioning skills.

In addition, it probably takes more than genes to cause the disorder. Scientists think interactions between genes and the environment are necessary for mental disorder to develop. Many environmental factors may be involved, such as exposure to viruses or malnutrition before birth, problems during birth, and other not yet known psychosocial factors.

 Different Brain Chemistry And Structure

 

Some mental disorders have been linked to an abnormal balance of special chemicals in the brain called neurotransmitters[1] like dopamine and glutamate, and possibly others. Chemical abnormalities are known to play a role in some mental disorders like schizophrenia. Neurotransmitters help nerve cells in the brain communicate with each other. If these chemicals are out of balance or are not working properly, messages may not make it through the brain correctly, leading to symptoms of mental disorder. In addition, defects in or injury to certain areas of the brain have also been linked to chemical abnormalities and some mental conditions.

Also, in small ways the brains of people with mental disorder look different than those of healthy people. For example, fluid-filled cavities at the centre of the brain, called ventricles, are larger in some people with mental disorder. The brains of people with the illness also tend to have less gray matter, and some areas of the brain may have less or more activity and in either case, one may have chemical pathology.

 Infections and Brain Damage

 

Certain infections have been linked to brain damage and the development of mental disorder or the worsening of its symptoms. For example, a condition known as paediatric autoimmune neuropsychiatric disorder (PANDA) associated with some species of streptococcus has been linked to the development of obsessive-compulsive disorder and other mental disorders in children (Garvey et al., 1998). There are a number of mental disorders that have been linked with microbial pathogens (Pearce, 2003). There have been links between infection by the parasite Toxoplasma gondii , HIV, cryptococcus among others and mental disorders, with the direction of causality presented invariably (Thomas et al., 2004; Alvarado-Esquivel, 2006; Vyas et al., 2007). A number of diseases of the white matter can cause symptoms of mental disorders (Walterfang et al., 2005). The current research on Lyme's Disease caused by a deer tick, and related toxins, is expanding the link between bacterial infections and The current research on Lyme's Disease caused by a deer tick, and related toxins, is expanding the link between bacterial infections and mental disorders.

 

 Brain Defects Or Injury

Defects in or injury to certain areas of the brain has also been linked to some mental disorders.

 Prenatal Damage

Some evidence suggests that a disruption of early fatal brain development or trauma that occurs at the time of birth -- for example, loss of oxygen to the brain -- may be a factor in the development of certain conditions, such as autism.

Higher rates of mood, psychotic, and alcohol and substance abuse disorders have been found following traumatic brain injury (TBI). Findings on the relationship between TBI severity and prevalence of subsequent mental disorders have been inconsistent, and occurrence has been linked to prior mental health problems as well as direct neurophysiological effects, in a complex interaction with personality and attitude and social influences (Fann et al., 2004).

  Alcohol and substance abuse

Long-term alcohol and substance abuse, in particular, has been linked to anxiety, depression, and paranoia. 

 Psychological Factors

 

A great many psychological factors have been identified and linked to mental disorders and the notable ones include:

§   Severe psychological trauma suffered as a child, such as emotional, physical, or sexual abuse

§   An important early loss, such as the loss of a parent

§   Neglect

§   Poor ability to relate to others

 Environmental Factors

 

Certain stressors within the environment can trigger a mental disorder in a susceptible person. These stressors may include:

§  Death or divorce.

§  A dysfunctional family life.

§  Living in poverty.

§  Feelings of inadequacy, low self-esteem, anxiety, anger, or loneliness.

§  Changing jobs or schools....

§  Social or cultural expectations (For example, a society that associates beauty with thinness can be a factor in the development of eating disorders.)

§  Alcohol and substance abuse by the person or the person's parents.

·        Neighbourhoods, society and culture. Problems in communities or cultures, including poverty, unemployment or underemployment, lack of social cohesion, and migration (especially among refugees), have been implicated in the development of mental disorders (Pilgrim et al., 2005; Glahn et al., 2007). Stresses and strains related to socioeconomic position (socioeconomic status (SES) or social class) have been linked to the occurrence of major mental disorders , with a lower or more insecure educational, occupational, economic or social position generally linked to more mental disorders (Muntaner et al., 2004). There have been mixed findings on the nature of the links and on the extent to which pre-existing personal characteristics influence the links. Both personal resources and community factors have been implicated, as well as interactions between individual-level and regional-level income levels (Lorant et al., 2003). The causal role of different socioeconomic factors may vary by country (Araya et al., 2003). Socioeconomic deprivation in neighbourhoods can cause worse mental health, even after accounting for genetic factors (Caspi et al., 2000). In addition, minority ethnic groups, including first or second-generation immigrants, have been found to be at greater risk for developing mental disorders, which has been attributed to various kinds of life insecurities and disadvantages, including racism (Chakraborty and McKenzie, 2002). The direction of causality is sometimes unclear, and alternative hypotheses such as the Drift Hypothesis sometimes need to be discounted.

·        Mental disorder has also been linked to the overarching social, economic and cultural system (Ihsan, 1995; Bergin and Richards, 2000; Fee, 2000 Krause, 2006).  A value system that promotes individualism, weakens social ties, and creates ambivalence towards children, is being spread or imposed via globalization, yet could adversely affect children's mental health.

·        Life events, stresses and relationships. Maltreatment in childhood and in adulthood, including abuse, physical, emotional abuse, domestic violence and bullying, has been linked to the development of mental disorder, through a complex interaction of societal, family, psychological and biological factors (Maughan and McCarthy,1997;Spataro et al., 2004; Teicher et al., 2006). Negative or stressful life events more generally have been implicated in the development of a range of mental disorders, including mood and anxiety disorders. The main risks appear to be from a cumulative combination of such experiences over time, although exposure to a single major trauma can sometimes lead to psychopathology, including PTSD. Resilience to such experiences varies, and a person may be resistant to some forms of experience but susceptible to others. Features associated with variations in resilience include genetic vulnerability, temperamental characteristics, cognitive set, coping patterns, and other experiences (Rutter, 2000).

 Other factors

 

Poor nutrition and exposure to pollutants, such as lead may play a role in the development of mental disorders. Poor general health has been found among individuals with severe mental disorders thought to be due to direct factors including diet, substance use, effects of medication and social economic disadvantages.

Relationship issues have consistently been linked to development of mental disorders, with continued debate of the school, work and home environmental being of relative importance and not forgetting the peer group.  Parenting skills, parental depression, divorce have been known to play a role in the aetiology of mental disorders. Early social privation or lack of ongoing harmonious secure committed relationships has been implicated both in childhood (including institutional care) and also through life span relationships. This is very evident during adolescence (Marano, 2003; Heinrich and Gullone, 2006).