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.
