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Philip Berman is a biological being. His thoughts and feelings are the results of biochemical and bioelectrical processes throughout his brain and body. Proponents of the biological model believe that a full understanding of Philip’s thoughts, emotions, and behavior must therefore include an understanding of their biological basis. Not surprisingly, then, they believe that the most effective treatments for Philip’s problems will be biological ones.

Adopting a medical perspective, biological theorists view abnormal behavior as an illness brought about by malfunctioning parts of the organism. Typically, they point to problems in brain anatomy or brain chemistry as the cause of such behavior.

Brain Anatomy and Abnormal Behavior The brain is made up of approximately 100 billion nerve cells, called neurons, and thousands of billions of support cells, called glia (from the Greek word for “glue”). Within the brain large groups of neurons form distinct areas, or brain regions. Toward the top of the brain, for example, is a cluster of regions, collectively referred to as the cerebrum, which includes the cortex, corpus callosum, basal ganglia, hippocampus, and amygdala (see Figure 2.1). The neurons in each of these brain regions control important functions. The cortex is the outer layer of the brain, the corpus callosum connects the brain’s two cerebral hemispheres, the basal ganglia plays a crucial role in planning and producing movement, the hippocampus helps regulate emotions and memory, and the amygdala plays a key role in emotional memory. Clinical researchers have discovered connections between certain psychological disorders and problems in specific areas of the brain. One such disorder is Huntington’s disease, a disorder marked by violent emotional outbursts, memory loss, suicidal thinking, involuntary body movements, and absurd beliefs. This disease has been traced to a loss of cells in the basal ganglia and cortex.

Brain Chemistry and Abnormal Behavior Biological researchers have also learned that psychological disorders can be related to problems in the transmission of messages from neuron to neuron. Information is communicated throughout the brain in the form of electrical impulses that travel from one neuron to one or more others. An impulse is first received by a neuron’s dendrites, antenna-like extensions located at one end of the neuron. From there it travels down the neuron’s axon, a long fiber extending from the neuron’s body. Finally, it is transmitted through the nerve ending at the end of the axon to the dendrites of other neurons (see Figure 2.2).

But how do messages get from the nerve ending of one neuron to the dendrites of another? After all, the neurons do not actually touch each other. A tiny space, called the synapse, separates one neuron from the next, and the message must somehow move across that space. When an electrical impulse reaches a neuron’s ending, the nerve ending is stimulated to release a chemical, called a neurotransmitter, that travels across the synaptic space to receptors on the dendrites of the neighboring neurons. After binding to the receiving neuron’s receptors, some neurotransmitters give a message to receiving neurons to “fire,” that is, to trigger their own electrical impulse. Other neurotransmitters carry an inhibitory message; they tell receiving neurons to stop all firing. As you can see, neurotransmitters play a key role in moving information through the brain.

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Researchers have identified dozens of neurotransmitters in the brain, and they have learned that each neuron uses only certain kinds. Studies indicate that abnormal activity by certain neurotransmitters can lead to specific mental disorders. Depression, for example, has been linked to low activity of the neurotransmitters serotonin and norepinephrine. Perhaps low serotonin activity is partly responsible for Philip Berman’s pattern of depression and rage.

In addition to focusing on neurons and neurotransmitters, researchers have learned that mental disorders are sometimes related to abnormal chemical activity in the body’s endocrine system. Endocrine glands, located throughout the body, work along with neurons to control such vital activities as growth, reproduction, sexual activity, heart rate, body temperature, energy, and responses to stress. The glands release chemicals called hormones into the bloodstream, and these chemicals then propel body organs into action. During times of stress, for example, the adrenal glands, located on top of the kidneys, secrete the hormone cortisol to help the body deal with the stress. Abnormal secretions of this chemical have been tied to anxiety and mood disorders.

Sources of Biological Abnormalities Why do some people have brain structures or biochemical activities that differ from the norm? Three factors have received particular attention in recent years—genetics, evolution, and viral infections.

GENETICS AND ABNORMAL BEHAVIOR Abnormalities in brain anatomy or chemistry are sometimes the result of genetic inheritance. Each cell in the human brain and body contains 23 pairs of chromosomes, with each chromosome in a pair inherited from one of the person’s parents. Every chromosome contains numerous genes—segments that control the characteristics and traits a person inherits. Altogether, each cell contains around 30,000 genes (NIH, 2015; Emig et al., 2013). Scientists have known for years that genes help determine such physical characteristics as hair color, height, and eyesight. Genes can make people more prone to heart disease, cancer, or diabetes and perhaps to possessing artistic or musical skill. Studies suggest that inheritance also plays a part in mood disorders, schizophrenia, and other mental disorders. It appears that in most cases, several genes combine to help produce our actions and reactions, both functional and dysfunctional.

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The precise contributions of various genes to mental disorders have become clearer in recent years, thanks in part to the completion of the Human Genome Project in 2000. In this major undertaking, scientists used the tools of molecular biology to map, or sequence, all of the genes in the human body in great detail. With this information in hand, researchers hope eventually to be able to prevent or change genes that help cause medical or psychological disorders.

EVOLUTION AND ABNORMAL BEHAVIOR Genes that contribute to mental disorders are typically viewed as unfortunate occurrences—almost mistakes of inheritance. The responsible gene may be a mutation, an abnormal form of the appropriate gene that emerges by accident. Or the problematic gene may be inherited by an individual after it has initially entered the family line as a mutation. According to some theorists, however, many of the genes that contribute to abnormal functioning are actually the result of normal evolutionary principles (Sipahi et al., 2014; Fábrega, 2010).

In general, evolutionary theorists argue that human reactions and the genes responsible for them have survived over the course of time because they have helped individuals to thrive and adapt. Ancestors who had the ability to run fast, for example, or the craftiness to hide were most able to escape their enemies and to reproduce. Thus, the genes responsible for effective walking, running, or problem solving were particularly likely to be passed on from generation to generation to the present day.

Similarly, say evolutionary theorists, the capacity to experience fear was, and in many instances still is, adaptive. Fear alerted our ancestors to dangers, threats, and losses so that persons could avoid or escape potential problems. People who were particularly sensitive to danger—those with greater fear responses—were more likely to survive catastrophes, battles, and the like and to reproduce and pass on their fear genes. Of course, in today’s world, pressures are more numerous, subtle, and complex than they were in the past, condemning many individuals with such genes to a near-endless stream of fear and arousal. That is, the very genes that helped their ancestors to survive and reproduce might now leave these individuals particularly prone to fear reactions, anxiety disorders, or related psychological disorders.

The evolutionary perspective is controversial in the clinical field and has been rejected by many theorists. Imprecise and at times impossible to research, this explanation requires leaps of faith that many scientists find unacceptable.

VIRAL INFECTIONS AND ABNORMAL BEHAVIOR Another possible source of abnormal brain structure or biochemical dysfunctioning is viral infections. As you will see in Chapter 14, for example, research suggests that schizophrenia, a disorder marked by delusions, hallucinations, or other departures from reality, may be related to exposure to certain viruses during childhood or before birth (Liu et al., 2014; Arias et al., 2012). Studies have found that the mothers of many individuals with this disorder contracted influenza or related viruses during their pregnancy. This and related pieces of circumstantial evidence suggest that a damaging virus may enter the fetus’ brain and remain dormant there until the individual reaches adolescence or young adulthood. At that time, the virus may produce the symptoms of schizophrenia. During the past decade, researchers have sometimes linked viruses to anxiety, depressive, and bipolar disorders, as well as to psychotic disorders (Liu et al., 2014).

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Biological practitioners look for certain kinds of clues when they try to understand abnormal behavior. Does the person’s family have a history of that behavior, and hence a possible genetic predisposition to it? (Philip Berman’s case history mentions that his mother was once hospitalized for depression.) Is the behavior produced by events that could have had a physiological effect? (Philip was having a drink when he flew into a jealous rage at the restaurant.)

Once the clinicians have pinpointed physical sources of dysfunctioning, they are in a better position to choose a biological course of treatment. The three leading kinds of biological treatments used today are drug therapy, electroconvulsive therapy, and psychosurgery. Drug therapy is by far the most common of these approaches.

In the 1950s, researchers discovered several effective psychotropic medications, drugs that mainly affect emotions and thought processes. These drugs have greatly changed the outlook for a number of mental disorders and today are used widely, either alone or with other forms of therapy. However, the psychotropic drug revolution has also produced some major problems. Many people believe, for example, that the drugs are overused. Moreover, while drugs are effective in many cases, they do not help everyone. Thus many people seek out a biological alternative to drug therapy—the enormously popular herbal supplements (see InfoCentral below).

Four major psychotropic drug groups are used in therapy: antianxiety, antidepressant, antibipolar, and antipsychotic drugs. Antianxiety drugs, also called minor tranquilizers or anxiolytics, help reduce tension and anxiety. Antidepressant drugs help improve the mood of people who are depressed. Antibipolar drugs, also called mood stabilizers, help steady the moods of those with a bipolar disorder, a condition marked by mood swings from mania to depression. And antipsychotic drugs help reduce the confusion, hallucinations, and delusions of psychotic disorders, disorders (such as schizophrenia) marked by a loss of contact with reality.

Psychotropic drugs, like all medications, reach the marketplace only after systematic research and careful review. It takes an average of 12 years and hundreds of millions of dollars for a pharmaceutical company in the United States to bring a newly identified chemical compound to market. Along the way, the drug is vigorously tested in study after study—first on animals and then on humans—to determine its efficacy, safety, dosage, and side effects, until finally it receives approval by the U.S. Food and Drug Administration. Only 3 percent of newly discovered chemical compounds make it to animal testing, only 2 percent of animal-tested compounds reach human testing, and only 21 percent of human-tested drugs are eventually approved (FDA, 2014).

A second form of biological treatment, used primarily on depressed patients, is electroconvulsive therapy (ECT). Two electrodes are attached to a patient’s forehead, and an electrical current of 65 to 140 volts is passed briefly through the brain. The current causes a brain seizure that lasts up to a few minutes. After seven to nine ECT sessions, spaced two or three days apart, many patients feel considerably less depressed. The treatment is used on tens of thousands of depressed persons annually, particularly those whose depression fails to respond to other treatments (Dukart et al., 2014).

A third form of biological treatment is psychosurgery, or neurosurgery, brain surgery for mental disorders. It is thought to have roots as far back as trephining, the prehistoric practice of chipping a hole in the skull of a person who behaved strangely. Modern procedures are derived from a technique first developed in the late 1930s by a Portuguese neuropsychiatrist, António Egas Moniz. In that procedure, known as a lobotomy, a surgeon would cut the connections between the brain’s frontal lobes and the lower regions of the brain. Today’s psychosurgery procedures are much more precise than the lobotomies of the past. Even so, they are considered experimental and are used only after certain severe disorders have continued for years without responding to any other form of treatment.

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Today the biological model enjoys considerable respect. Biological research constantly produces valuable new information. And biological treatments often bring great relief when other approaches have failed. At the same time, this model has its shortcomings. Some of its proponents seem to expect that all human behavior can be explained in biological terms and treated with biological methods. This view can limit rather than enhance our understanding of abnormal functioning. Our mental life is an interplay of biological and nonbiological factors, and it is important to understand that interplay rather than to focus on biological variables alone.

Another shortcoming is that several of today’s biological treatments are capable of producing significant undesirable effects. Certain antipsychotic drugs, for example, may produce movement problems such as severe shaking, bizarre-looking contractions of the face and body, and extreme restlessness. Clearly such costs must be addressed and weighed against the drug’s benefits.