Psychology Psychological Disorders Substance-Related & Schizophrenia
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Substance-Related Disorders
The DSM describes many substance-related disorders, which occur when a person is intoxicated by, withdrawing from, using, abusing, or dependent on one or more drugs. Two common types of substance-related disorders are substance abuse and substance dependence.
Substance Abuse
The DSM defines substance abuse as a maladaptive pattern of drug use that results in repeated negative consequences such as legal, social, work-related, or school-related problems. A drug abuser may even use drugs in situations in which it is physically dangerous to do so.
Substance Dependence
Substance dependence, or drug addiction, involves continuing to use a drug despite persistent physical or psychological costs. A person who is addicted to drugs may make several unsuccessful attempts to give up the drug and may even develop tolerance for the drug. Tolerance is the gradual need for more and more of the drug to get the same effect. The person may also experience withdrawal symptoms such as sweating, nausea, muscle pain, shakiness, and irritability when he or she stops taking the drug.
Etiology of Substance-Dependence
Many researchers believe biology and environment interact to produce substance dependence.
Biological Influences
Several lines of research have examined genetic predispositions to drug dependence. Researchers think there may be a genetic predisposition to one particular type of alcoholism: the type that begins in adolescence and that is associated with impulsive, antisocial, and criminal behavior. With other types of alcoholism, many genes may interact to play a role.
Genes may influence traits such as impulsivity, which can make a person more likely to become alcoholic. Genes may also influence the level of dopamine in the brain. Researchers have suggested that high dopamine levels may in turn influence the susceptibility to alcoholism.
Just as biological factors may make a person susceptible to dependence, heavy use of drugs can affect a person’s biological makeup. For example, excessive drug use can reduce the number of dopamine receptors in the brain. Since dopamine is involved in feeling pleasure, the reduced number of receptors can then make a person dependent on the drug. The person will crave more of the drug in order to feel the same amount of pleasure.
Environmental Influences
Research findings suggest that certain environmental factors play a key role in substance dependence:
- Cultural norms: The pattern of drug dependence varies according to cultural norms. For example, alcohol dependence is rarer in countries where children learn to drink responsibly and in moderation and where excessive drinking by adults is considered improper. Alcohol dependence is more common in societies that condone adult drunkenness and forbid children to drink.
- Social policy: Governmental policies that totally prohibit alcohol consumption tend to increase rates of alcohol dependence.
- Variation in symptoms: The existence of withdrawal symptoms after discontinuing a drug depends on many factors, including a person’s expectations and context. This suggests that dependence is not just a biological phenomenon.
- Reasons for drug use: A person’s tendency toward drug addiction depends not only on the properties of the drug but also on the reasons a person uses the drug. For example, people who receive prescription narcotics in hospitals for postsurgical pain may not become addicted, while others who use narcotics to escape stress may become addicted.
Schizophrenia
Schizophrenia is one of several psychotic disorders described in the DSM. People with psychotic disorders lose contact with reality and often have delusions or hallucinations. People with schizophrenia have a wide range of symptoms, which can be classified into positive or negative symptoms.
Positive Symptoms
Positive symptoms involve the presence of altered behaviors. Examples of positive symptoms include delusions, hallucinations, disorganized speech, and disorganized behavior. Delusions are false beliefs that are strongly held despite contradictory evidence. Hallucinations are sensory or perceptual experiences that happen without any external stimulus. Hallucinations can occur in any sensory modality, but auditory hallucinations are most common in schizophrenia. Disorganized speech can also take many forms. For example, a person with schizophrenia may produce word salad, which consists of words and sentences strung together in an incoherent way. Examples of disorganized behavior include inappropriate gestures or laughter, agitated pacing, or unpredictable violence.
Negative Symptoms
Negative symptoms involve an absence or reduction of normal behavior. Negative symptoms include emotional flatness, social withdrawal, spare or uninflected speech, and lack of motivation.
Subtypes of Schizophrenia
Schizophrenia is classified into four subtypes, depending on the symptoms present at the time of evaluation:
- Paranoid type: Characterized by marked delusions or hallucinations and relatively normal cognitive and emotional functioning. Delusions are usually persecutory, grandiose, or both. Persecutory delusions involve a belief that one is being oppressed, pursued, or harassed in some way. Grandiose delusions involve the belief that one is very important or famous. This subtype usually happens later in life than the other subtypes. Prognosis may also be better for this subtype than for other subtypes.
- Disorganized type: Characterized by disorganized behavior, disorganized speech, and emotional flatness or inappropriateness.
- Catatonic type: Characterized by unnatural movement patterns such as rigid, unmoving posture or continual, purposeless movements, or by unnatural speech patterns such as absence of speech or parroting of other people’s speech.
- Undifferentiated type: Diagnosis given to a patient that does not meet criteria for paranoid, disorganized, or catatonic schizophrenia.
Etiology of Schizophrenia
As with other psychological disorders, researchers have studied the etiology of schizophrenia from different perspectives.
Biological Factors
Research suggests that genes, neurotransmitters, and brain abnormalities play a role in the onset of schizophrenia:
- Genetic predisposition: Substantial evidence suggests that there is a genetically inherited predisposition to schizophrenia. For example, there is a concordance rate of about 48 percent for identical twins. The concordance rate for fraternal twins is considerably less, about 17 percent. Concordance rate refers to the percentage of both people in a pair having a certain trait or disorder. A person who has two parents with schizophrenia has about a 46 percent chance of developing schizophrenia. This probability is very high compared to the roughly 1 percent chance of developing schizophrenia in the general population.
- Neurotransmitters: Some researchers have proposed that schizophrenia is related to an overabundance of the neurotransmitter dopamine in the brain. Other researchers have suggested that both serotonin and dopamine may be implicated. The neurotransmitter glutamate may also play a role in the disorder. Underdevelopment of glutamate neurons results in the overactivity of dopamine neurons.
- Brain structure: Some researchers have suggested that schizophrenia may involve an inability to filter out irrelevant information, which leads to being overwhelmed by stimuli. With this idea in mind, researchers have looked for brain abnormalities in schizophrenia patients. The brains of people with schizophrenia do differ structurally from the brains of normal people in several ways. For example, they are more likely to have enlarged ventricles, or fluid-filled spaces. They are also more likely to have abnormalities in the thalamus and reduced hippocampus volume.
- Brain injury: Another line of research suggests that injuries to the brain during sensitive periods of development can make people susceptible to schizophrenia later on in life. For example, researchers believe that viral infections or malnutrition during the prenatal period and complications during the birthing process can increase the later risk of schizophrenia. Some researchers have suggested that abnormal brain development during adolescence may also play a role in schizophrenia.
Stress
Many researchers believe stress plays a role in bringing on schizophrenia in people who are already biologically vulnerable to this disorder.
