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Abnormal Psychology


Main Theories of Abnormal Behavior


Biological Theory

Deficits or defects in the structural or functional integrity of the nervous system lead to abnormal behavior. Types of biological abnormalities include:

  1. Defective genes: Each chromosome contains thousands of genes (carriers of DNA) that influence psychological and physical development. Defective genes may adversely affect development (e.g., trisomy causes Down syndrome).

    • Behavior genetics: the study of individual differences in behavior that are caused by differences in genotype (a person’s genetic makeup). Typically, it takes a combination of several altered genes to cause a disorder.

  2. Structural brain abnormalities: occur when areas of the brain have not developed optimally or have undergone pathological changes (e.g., the ventricles, which are the fluid-filled portions of the cortex, often are larger in schizophrenics).

  3. Neurotransmitter imbalances: The 100 billion neurons in the central nervous system (CNS) communicate by chemical messengers called neurotransmitters, which can become imbalanced. Biological approaches to treatment focus mainly on medications that address neurotransmitter imbalances.

    1. Neurotransmitters (e.g., serotonin, dopamine, norepinephrine, GABA) are released into the synaptic cleft (the small gap between the axon of one and the dendrites of the receiving or postsynaptic neuron). They regulate level of mood, anxiety, and cognitive functioning. Factors affecting imbalance include:

      1. Number, distribution, and functioning of receptors on the dendrites (the receiving branches of the neuron)

      2. Reuptake: the amount of neurotransmitter in the synaptic cleft, or vesicle, that is reabsorbed by the releasing neuron

      3. Degradation: the process by which a neurotransmitter is broken down by enzymes released by the receiving neuron

  4. Hormones: chemicals secreted by the endocrine glands (e.g., pituitary). They play a role in the functioning of the nervous system and in the regulation of behavior (e.g., during adolescence, changes in the hypothalamic-pituitary-adrenal [HPA] axis are involved in the increase in cortisol, a stress-related hormone).

    • Functioning of neurotransmitters and endocrine glands is based on both biological factors and environmental stressors.

  5. Methods used to assess the contribution of biological factors:

    1. Twin studies: Concordance rates in monozygotic (100% genes in common) and dizygotic twins (50% genes in common) allow researchers to tease apart genetic causes. If the concordance rate (the rate at which one twin has the disorder and the other does, too) is higher in monozygotic vs. dyzgotic twins, then the argument is made for a stronger genetic component to the illness.

    2. Studies of family history: A researcher identifies those people with the disorder (probands), examines family trees, and compares that information with controls, to see what percentage of first-degree relatives also have the disorder. The problem is that one cannot tease apart genetic and environmental causes.

    3. Adoption studies: comparisons of rates of the disorder in the adoptive relatives vs. biological relatives of the adoptees. This helps tease apart genetic and environmental causes.


Psychological Theories

  1. Psychodynamic: refers to the conflict of forces in the mind. Sigmund Freud, the father of psychoanalysis, was the founder of modern psychodynamic therapy.

    1. Key assumptions include:

      1. Psychic determinism: Mental life is lawful (i.e., the apparently random sequences of thoughts are not really random but are guided and connected by underlying motives).

      2. Unconscious motivation: Most of mental life, particularly wishes, operates outside of awareness

    2. The mind is organized on the basis of conflicts between:

      1. Id: the unconscious wishes

      2. Ego: coping and defense mechanisms

      3. Superego: the conscience

    3. Instinctual drives: Freud posited that sex (broadly defined as physical urges) and aggression are the two main instinctual drives.

    4. Defenses: If a person has wishes, desires, and fantasies (based on these drives) that he/she regards as unacceptable and that arouse anxiety, he/she deals with them by means of defense mechanisms.

      • Defense mechanism: any mental process or behavior that can be used to ward off negative feelings (see chart)

      Defense Mechanism   Description


        Keeping unacceptable wishes from consciousness


        Attributing unacceptable wishes to someone else (e.g., “I don’t hate you—you hate me”)

      Reaction formation

        Transforming unacceptable wishes into their opposite (e.g., being saccharine-sweet rather than hostile)


        Redirecting a feeling from one person to another


        Reverting to behavior from an earlier stage in development to avoid anxiety


        Presenting a socially acceptable reason for behavior as a way of avoiding the real reason


        Disavowing an action, thought, or feeling; refusing to admit to an aspect of reality


        Avoiding unpleasant feelings by adopting a highly ideational approach

      Isolation of affect

        Keeping ideas and their feelings they excite separate in one’s mind


        Redirecting unacceptable impulses to socially desirable behavior

    5. Symptoms arise when threatening wishes are too strong and/or defenses are too weak.

    6. Freud described four psychosexual stages of development: oral, anal, phallic, and genital. Excessive gratification or deprivation at a given stage can result in:

      1. Fixation: stagnation at that stage

      2. Regression: a return to aspects of a given stage at times of stress (e.g., reverting to thumb-sucking following the birth of a sibling)

  2. Behavioral: focus on observable behavior rather than on the person’s inner mental life. Abnormal behavior is based on learning and environmental experiences.

    1. Classical conditioning (Pavlov): The pairing of contiguous events makes organisms learn associations between things, creating involuntary responses to stimuli

      Elements of classical conditioning:

      1. UCS (unconditioned stimulus, food) => UCR (unconditioned response, salivation to food)

      2. UCS (food) + CS (conditioned stimulus, bell)=> UCR (salivation to food)

      3. CS (bell) => CR (conditioned response, salivation to bell)

        • Extinction of the conditioned response happens when, over the course of many trials, the sound of the bell is not followed by food.

    2. Operant conditioning: the shaping of behaviors via reinforcers (i.e., rewards and punishments).

      1. Positive reinforcers: rewards that increase the probability of behavior

      2. Negative reinforcers: the removal of aversive stimuli that increase the probability of behavior (e.g., a social phobic feels relieved of anxiety when she avoids parties, so she continues to avoid)

      3. Punishment: negative consequences that decrease the probability of behavior

      4. Thorndike’s law of effect: behaviors followed by punishment are weakened; behaviors followed by rewards are strengthened.

      5. Extinction is more difficult with a partial, in comparison with a continuous, reinforcement schedule.

    3. Modeling: learning based on observing others. Even in the absence of obvious reinforcers, we learn and behave by watching and imitating others. We are influenced by the rewards and punishments others receive for their actions.

  3. Cognitive: One’s misconceptions of the world and misinterpretations of experience lead to beliefs and thoughts that cause negative feelings and behaviors, making one more vulnerable to abnormalities.

    1. Dysfunctional ideas and causal attributions are distorted, self-defeating, and irrational. These incorrect thoughts are based on faulty schemas (organizations of beliefs and assumptions).

    2. Beck and Ellis are major proponents of the cognitive view. Ellis focuses on common irrational beliefs that must be overcome (e.g., “Everyone must love me”). Beck emphasizes the cognitive triad in depressed patients (having a negative view of themselves, the world, and their future).

  4. Humanistic/existential views: focus on man’s mortality, responsibility for decision-making, and his search for meaning in life. Proponents believe that disorders arise when people feel compelled to conform to parental/societal demands instead of acting with authenticity in the pursuit of their own true values and goals. Authencity is more apt to promote self-actualization (the fulfillment of one’s potential).

  5. Sociocultural perspectives

    1. Focuses on the impact of social forces, family and cultural influences, and failures of society on individual mental health

    2. Failure of support system: family, friends, community in times of stress (e.g., poverty, gender or racial discrimination, lack of opportunity)


Bio-Psycho-Social Integration

Abnormality is a function of the interaction of these three sets of factors and the vulnerability they create in the individual.


The Diathesis-Stress Model

Individual differences in vulnerability (diathesis), due to biological and psychological factors, interact with stressors in the environment. Proponents believe that particular combinations of diathesis and stress cause abnormal behavior.

  • High stress and low diathesis or low stress and high diathesis both can lead to psychological disturbance.