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Biological and Psychological Models of Abnormality



The many different models used to explain the nature and treatment of mental illness compound the problems of defining and classifying abnormal behaviour. Five major schools of thought are summarised below.


The biological (medical) model

The medical of abnormality model has dominated the psychiatric profession since the last century . The underlying assumption of this model is that mental illnesses resemble physical illnesses and can therefore be diagnosed and treated in a similar way. Just as physical illnesses are caused by disease producing germs, genetic factors, biochemical imbalances or changes to the nervous system, it is assumed that this is also true of mental illnesses. Because it assumes that mental disorders arise from such physical causes, the medical model is therefore a biological model.



A patient presenting with symptoms of depression (e.g., extreme tiredness, difficulty in sleeping, lack of interest in life, possible suicidal tendencies) would be diagnosed as having a problem resulting from an imbalance of brain chemicals. This could be corrected by prescribing drugs to restore the balance, or in severe cases ECT (electro convulsive therapy).


Evaluation of the biological model

Assuming that psychological disorders are the result of biological factors is not without its problems. For example, the classification of physical illnesses involves observation and measurement of objective symptoms such as broken bones, fever, blood pressure etc., whereas with mental illnesses, the symptoms are much more subjective — e.g., feelings of despair, lack of energy or hearing voices. These cannot be easily measured, so the clinician must make a judgement based largely on experience.

Also, the difference between physical and mental illness is that diagnosis of physical illness can normally relate to the causes of the problem (known as aetiology). For example, measuring blood sugar levels could check a diagnosis of diabetes. However as we will see, the causes of many mental illnesses are unknown. This has an important consequence for treatments based on the biomedical model, as they can be criticised as focusing only on the symptoms of mental disorders and not the causes.

Finally, humanistic and existentialist biased therapists aften point out that the medical model in encouraging the view that people who suffer from mental disorders are ‘patients', hands responsibility over to doctors and other professionals. In this way the individual is discouraged from taking control of his or her own life and as a consequence his or her problems will ultimately remain unresolved.


Against these negative criticisms could be set the undeniable progress that has been made in understanding the biological basis of many mental disorders (especially schizophrenia) and the successful development of bio-medical treatments.


In summary, the strengths of the biological model are:

  • The model is based on well established sciences such as medicine
  • There is evidence that biochemical and genetic factors are associated with some mental illnesses: schizophrenia, for example
  • It provides a structured and logical system of diagnosis and treatment
  • If mental illness has a physical cause, patients cannot be blamed — the person is not responsible for the abnormal functioning

The weaknesses of the biological model are:

  • The model does not explain the success of purely psychological treatments for mental illnesses
  • For most mental illnesses, there is no definite proof of a physical cause
  • The model does not include consideration of social and cultural factors which do seem to be statistically linked to mental illness, e.g., higher rates of mental illness amongst the poor
  • Even if physical changes are associated with mental disorders, it is not clear whether they are the cause or the effect of the illness


The psychodynamic model

The psychodynamic model was first formulated by Sigmund Freud at the end of the 19th century and since that time has had an enormous influence on the entire area of abnormal psychology. It still offers for many therapists a preferred alternative to biological approaches to abnormality. The core assumption of this approach is that the roots of mental disorders are psychological. They lie in the unconscious mind and are the result the failure of defence mechanisms to protect the self (or ego) from anxiety. Many of these intrapsychic conflicts involve basic biological instincts, especially sexual ones. Many adult problems are reflections of these earlier conflicts, particularly those stemming from infancy and early childhood (such as the Oedipus conflict).


Treatments based on the psychodynamic model focus on gaining access to the unconscious and exploring the conflicts with the patient so that they are able to confront them and resolve them in an adult way. The emphasis is on the patient gaining insight into the origins of their problems. This technique is known as psychoanalysis. The method of psychoanalysis first developed by Freud is still practised, but perhaps more common today are the psychodynamic psychotherapies. These share the fundamental principles of psychoanalysis, but are more eclectic and relaxed in their treatment of patients.


A patient presenting with anxiety symptoms would be encouraged to explore his past in order to discover problems occurring during one of the psychosexual stages (oral, anal, phallic and genital). In order to deal with this problem the patient has used ego-defence mechanisms, such as repression or denial. These have taken up a lot of psychic energy, leaving the patient with fewer resources to deal with everyday life. The anxiety itself may have become directed towards someone or something else in the patient’s world (displacement). Treatment would involve, among other things, helping the patient to gain insight into the causes of his anxiety.


Evaluation of the psychoanalytic model

The psychodymamic model has a number of strengths which account for its enduring popularity:

  • Many observations of psychodynamic therapists appear to be borne out in everyday life, e.g., defence mechanisms
  • Many people with psychological disturbances do recollect childhood traumas
  • Freudian theory provides a comprehensive framework to describe human personality
  • Freud ‘rehumanised’ the distressed, making their suffering more comprehensible to the rest of society
  • By developing a method of treatment, Freud encouraged a more optimistic view regarding psychological distress. Mental illness could, in some cases at least, be treated!

Weaknesses of the psychoanalytic model are:

  • The tendency to ignore the patient’s current problems by focusing on past conflicts (though this is not true of many later versions of psychoanalysis)
  • A lack of scientific evidence concerning major theoretical assumptions
  • As the source of many of the conflicts are often parents, there is a tendency to give a lot of responsibility to parents for the psychological health of their children
  • Psychodynamic theory underestimates the role of situation and context, and overemphasises internal instincts and conflicts


The behavioural model

The behaviourist approach dominated psychology in the first half of this century, especially in the USA. The goals of behaviourism were to move psychology toward a scientific model, which focused on the observation and measurement of behaviour. Its assumptions were that behaviour is primarily the result of the environment rather then genetics (or instincts) and so the behaviourists reject the view that abnormal behaviour has a biological basis. Like the psychodynamic theorists, behaviourists have a deterministic view of mental disorders: they believe that our actions are largely determined by our experiences in life. However, unlike Freud, they see abnormal behaviour is a learned response (through conditioning) and not as the result of mysterious (and they would argue unknowable) unconscious processes. While much of our behaviour is adaptive, helping us to cope with a changing world, it is also possible to learn behaviours that are abnormal and undesirable. However, such maladaptive learning can be treated by changing the environment so that un-learning could take place.


A patient’s fear (phobia) of heights would be explained through the process of classical conditioning. Some time in the past, she would have learned to associate the emotion of fear with the stimulus of being in a high place through a chance association between the two stimuli. As a result, she would avoid heights, and therefore not have the opportunity to relearn the association in a more adaptive way. Treatment would involve desensitising the fear through conditioning techniques.


Evaluation of the the behavioural model

Among the strengths of the model are:

  • It has led to the development of specific behavioural therapies, many of which have had high success rates
  • It is widely regarded as lending itself to scientific study and evaluation
  • Proponents of the model argue that once the symptoms of an illness are alleviated, the complaint disappears

Weaknesses include:

  • The model is reductionist in the sense that it reduces the complexity of human behaviour to behavioural responses to environmental stimuli
  • Only the symptoms of illnesses are treated, not the underlying causes
  • The model provides a limited view of the causes of mental illness and does not explain the evidence relating to genetic predispositions to mental illness
  • Environmental causes of abnormal behaviours are only rarely discovered in patients


One important extension of the behaviourist approach is known as social learning theory (SLT). These theorists (e.g. Bandura) argue that observation and imitation (known as modelling) are an important forms of learning neglected by the early behaviourists. Thus maladaptive behaviour can be learned from poorly functioning parents through imitation. But it can also be treated by therapies based on modelling (for example a person with a snake phobia might learn from watching a person handle snakes). Because many therapists who use this approach act as a bridge between the behaviourist and the cognitive approaches, they are usually known as cognitive-behavioural therapists.


The cognitive model

The cognitive approach is both an outgrowth from, and a reaction to, the behaviourist approach. The basic assumption of the cognitive approach holds that mental events cause behaviour in that we interpret our environment before we react to it. In the case of abnormal behaviour, it is the interpretations and disordered cognitions that lead to the behaviour. Emotional problems can be attributed to distortions in our cognitions or thinking processes. These distortions are in the form of overgeneralisations, irrational beliefs, illogical errors or negative thoughts. The focus of treatment is on understanding the disordered thoughts and working with the patient to change these.



A patient suffering from a depressed mood after failing a driving test may be having negative thoughts not only about that specific failure but may be generalising those to other areas of her life. She may believe she is a failure in all aspects of her life and will never be successful again. These thoughts are irrational and polarised, and the therapist would strive to teach the patient ways of changing her thoughts. The therapist might also emphasise the importance of increasing positive reinforcements, and suggest ways in which this might be achieved.


Evaluation of the cognitive model:


Supporters of the cognitive approach claim that the strengths include:

  • There is much evidence of maladaptive thought processes in people with psychological disorders
  • This model promotes psychological well being by teaching people the means of control over their own lives

On the other hand, weaknesses of the cognitive model:

  • The disordered cognitions may be a result of the disorder, not the cause
  • The emphasis on the individual draws attention away from social support systems and the need to locate the causes of psychological distress in wider social, political and cultural contexts


The humanistic model

Sometimes referred to as ‘the third force in psychology’, the humanistic movement was a reaction against the determinism of the psychodynamic and behaviourist paradigms. It attempted to focus more on the individual as a whole person. According to Carl Rogers and other leading figures in this movement, people are rational beings, able to make their own choices, and are motivated toward a state of fulfilment. Psychological problems occur when people experience an incongruence between their real self and their ideal self. This generates a feeling of low self-worth. The humanistic model does not believe in labelling people by diagnosing them as having specific mental disorders. Every individual’s problems are seen as unique and the therapy lies in providing nurturing therapeutic conditions which enable the person to find his/her own way forward in dealing with problems.



An individual with feelings of despair and a lack of motivation to live would be understood in terms of a low sense of self-worth, perhaps to do with the lack of a nurturing environment. This has led to them losing touch with their true self. They are valuing themselves in overly negative ways, and feel that they are unacceptable and unlovable as a person. In order to get in touch with their true self, it is necessary to experience conditions that offer empathy, acceptance and genuine understanding.


Strengths of the humanistic model:

  • There is a large body of research, particularly case histories, to back up the claims of the humanistic model
  • The model offers an optimistic view of personality
  • It is regarded as an ethical model because it focuses on the person rather than the diagnosis
  • The model facilitates the human capacity for self-cure

Weaknesses of the humanistic model:

  • The focus on the individual carries the assumption that people should be able to help themselves, and may neglect important environmental and social factors (e.g., poverty and discrimination)
  • Some disorders requiring medical treatment may go untreated due to the reluctance to diagnose
  • The model tends to espouse western ideals of individuality and freedom, which may not take into account more collectively based cultures.




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Comments (1)

rasimoguzhan said

at 1:03 pm on Mar 1, 2019

Hello there,
Thanks for sharing.

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