Introduction chapter 2.

 If Mariella had lived centuries ago, demonic possession might have been a common explanation for her problems. Scientists and mental health professionals today, however, focus on a person’s biology, environment, and other factors to help people like Mariella. Scientists and mental health professionals develop perspectives or models—ways of looking at things—to piece together why someone like Mariella has problems. Perspectives or models are systematic ways of viewing and explaining what we see in the world. When you try to explain high prices for an item, you might think about the economic model of supply and demand to conclude everyone wants the item, but supplies are limited. Or if a friend of yours is sick, you might think about the disease model of germ theory to ask whether she was around a sick person or if she ate spoiled food.

Mental health professionals use models to help explain unusual behavior or mental disorders in people like Mariella. Five main models to explain mental disorders are described in this chapter: • The biological model focuses on genetics, neurotransmitters, brain changes, and other physical factors. • The psychodynamic model focuses on internal personality characteristics. • The humanistic model focuses on personal growth, choice, and responsibility. • The cognitive-behavioral model focuses on specific thoughts and learning experiences. • The sociocultural model focuses on external environmental events and includes the family systems perspective.

These models dominate the mental health profession today and influence the way we think about, assess, and treat mental disorders (see Figure 2.1). Each model has strengths and weaknesses, but each provides mental health professionals with ways of understanding what is happening to someone like Mariella. In this chapter, we show how each model could be used to explain Mariella’s problems and help her. Many mental health professionals also integrate these models to study and explain mental disorders .

The Biological Model The biological model rests on the assumption that mental states, emotions, and behaviors arise from brain function and other physical processes. This model has been in use for centuries and is stronger than ever today. Read a newspaper or magazine, watch television, or go online—countless articles, documentaries, and advertisements are available about medications and other substances to treat mental conditions. Some drug or herb always seems available to cure depression, anxiety, or sexual dysfunction. Despite the incessant advertising, however, the biological model of mental disorder, including the use of medications, is supported by scientific research that links genetics, neurochemistry, and brain changes to various psychological problems. The biological model of mental disorder was pioneered by Emil Kraepelin (1856–1926), who noticed various syndromes or clusters of symptoms in people. Mariella had a cluster of symptoms that included concentration problems, oversleeping, sadness, and weight loss. Her symptom are commonly described within the syndrome of depression (Chapter 7). Kraepelin believed, as do many psychiatrists and other mental health professionals today, that syndromes and symptoms have biological causes. Kraepelin proposed two major types of mental disorders, each with different biological causes: dementia praecox (similar to schizophrenia, discussed in Chapter 12) and manic-depressive psychosis (similar to bipolar disorder, discussed in Chapter 7). Kraepelin also believed syndromes to be separate from one another, like mumps and measles, and that each syndrome has unique causes, symptoms, and outcomes. In Mariella’s case, her symptom of sadness seemed partly caused by her separation from home and led to outcomes such as poor grades. Kraepelin and many psychiatrists also believe each syndrome has its own biological cause. A psychiatrist may feel Mariella’s sadness was caused by depression that ran in her family (genetics), by a chemical (neurotransmitter) imbalance, or by some brain change. We discuss these biological causes next. Genetics Do you think Mariella’s sadness may have been present as well in some of her family members? Many mental disorders such as depression do seem to run in families. Genetic material may be involved when symptoms of a mental disorder are passed from parents to children. Genetic material refers to molecular “codes” contained in the nucleus of every human cell (Ahuja, 2014). Genes are the smallest units of inheritance that carry information about how a person will appear and behave. Genes carry information about hair and eye color, weight and height, and even vulnerability to diseases such as lung cancer or mental disorders such as depression. Human genes are located on 46 chromosomes or threadlike structures arranged in 23 pairs. A person’s chromosomes come half from the biological mother and half from the biological father. The genetic composition of a person is known as a genotype and is fixed at birth. Genotypes produce characteristics such as eye color that do not change over time. An observable characteristic of a person is known as a phenotype, which can change over time. Observable characteristics can include intelligence, as well as symptoms of a mental disorder such as difficulty concentrating. Phenotypes can change because they result from genetic and environmental influences. Your intelligence is partly determined by genetics from your parents but also by the type of education you received as a child. Scientists are interested in knowing which genetic and environmental influences impact the development of emotions, cognitions, and behavior (O’Connor, 2014). This research specialty is known as behavior genetics. Behavior geneticists are interested in the degree to which a mental disorder is determined by genetics. Heritability refers to the amount of variation in a phenotype attributed to genetic factors, often expressed as a number ranging from 0 to 1. Some mental disorders such as anxiety-related disorders have modest heritability, but many major mental disorders have more substantial genetic influences in their development (see Figure 2.2). Disorders with particularly high heritability include bipolar disorder and schizophrenia (Pearlson, 2015). Behavior geneticists also focus on what specific genes are inherited and how these genes help produce a mental disorder. Researchers in the field of molecular genetics analyze deoxytribonucleic acid (DNA)—the molecular basis of genes—to identify associations between specific genes and mental disorders. Molecular genetics is quite challenging for several reasons. First, most mental disorders are influenced by multiple genes, not just one. When you hear a media report that researchers found a gene for Alzheimer’s disease, keep in mind they likely found only one of many genes. Second, the same symptoms of a mental disorder may be caused by different genes in different people. Third, it is estimated that there are about 20,000 to 25,000 human protein-coding genes, so finding specific ones related to a certain disorder is like finding a needle in a haystack. Despite these challenges, advances in molecular genetics will likely lead to findings that help scientists determine how and if disorders are genetically distinct from one another. Knowledge of specific genes can also help researchers determine how genes influence physical changes in the body, which we discuss next.