Psychopathology is the study of psychological disorders, their natures and causes. Psychodynamic approach is one of the approaches, which explains the dynamics of behaviour, and what motivates a person.
The root of the abnormality is the effect of repression of unresolved conflicts between unconscious desires. The behaviour is motivated by unconscious desires. Conflict between needs is not resolved it may cause problems later e.g. phobia. Repression pushes distressing events into unconscious.
The psychodynamic approach was mainly initiated by Sigmund Freud, a Viennese doctor who specialised in neurology. Freud’s theory and approach were influenced by the ideas and society of his time.
According to Freud he suggested that unconscious forces and early experience are the prime motivators. As an example to mythology, the first being that when you repress memories for too long and do not deal with them you can develop psychological disorders known as neurosis and these can manifest as panic attacks, phobias obsessive behaviour and this can affect normal day-to-day behaviour, which becomes neurotic behaviour.
Freud’s principles based on the principles that psychological illness comes about from self-conscious emotions and thoughts from experiences in the past usually childhood, and because of this repression, unusual behaviour replaces what is being repressed. The patients are believed to be cured when they can admit that which is currently being repressed.
The psychodynamic refers to both his theories and those of his followers. The most common shared assumption was:

Unconscious processes
Psychodynamic conflict
Emotional drives
Development

THE PSYCHODYNAMIC APPROACH ASSUMPTIONS ARE THAT:

Our manners and thoughts are strongly affected by conscious motives.
Our manners and feelings as adults including psychological problems are rooted in our childhood experiences.
All behaviour has a reason generally unconscious, even slips of the tongue. As a result all behaviour is determined.

According to Freud, the personality is made up of three parts: The id- The unconscious, insatiable set of instincts with which people are born. The Id is pleasure- orientated and completely selfish. Ego: the conscious, rational part of the superego, then the last super- ego: the moral part of the personality concerned with right and wrong. The super-ego develops through the process of socialization when people learn moral standards and expectations of their culture. The id and the superego therefore are in direct conflict and need to be managed in a rational way.
Behaviour is motivated by two instinctual drives: Eros (the sex drive and life instinct) and Thanatos. (The aggressive drive and death instinct). Both these drives come from the “id”.
Parts of the unconscious mind (the id and superego) are in constant conflict with the conscious part of the mind (the ego)
Personality is shaped as the drives are modified by different conflicts at different times in childhood (during psychosexual development).
The two limitations to psychodynamic approach are that:

The psychodynamic approach is unscientific in its analysis of human behavior. As an example to Freud theories: are subjective and as much impossible to scientifically test. Which makes difficult to analyze or prove scientifically.
Most of the evidence for psychodynamic theories is taken from Freud’s case studies e.g. (little hans) this case study are based on studying one personal detail, i.e. his patients from Vienna aged middle women. This makes generalization to the wider population e.g. the whole world difficult. And the treatment relies on expert help. Too Deterministic (free little will).

The two strength of psychodynamic approach are that:

The psychodynamic approach therapies drew attention to the psychological causes of mental disorder. Individuals with disorders often had traumatic events in childhood.
Psychoanalysis has enormous explanatory power and has something to say on a huge variety of important topics.

It highlights the importance of the unconscious mind. No blame on individual much on the parents.
Helen has been referred to a therapist because of her weight gain. She is 20 years old and she is a chocoholic. She has eaten ten bars of chocolate a day since she split up with her partner. According to her mother, chocolate has been a major ingredient in Helen’s diet for more than 18 years.
The behaviour approach is based on the concept of explaining behaviour through observation, and the belief that our environment is what causes us to behave differently or suffer.
The behavioural approach is seen as the effect of learning from the environment. As an example when the person has been placed in abnormal environment, they learn to act in abnormal ways. The result of learning the behaviour is learnt via stimulus response links. According to Helen behaviour, she might have acquired this behaviour through results from a set of learning experiences brought by the person’s environment. For example, Helen might have had a traumatic experience that she now associate with certain situations e.g. (classical conditioning) Helen might have also learned the behaviour through social learning and this limiting the models.
The behaviour model based on the belief that outside behaviour and reactions are mainly responsible for psychological illness and that in order to treat the illness, dysfunctional behaviour/ reactions need to be changed. The main categories of behaviourism are:
Classical conditioning: Pavlou’s Theory 1972 demonstrated how a dog was trained to associate food with sound of a bell (noise). This process links together a natural response to unconditional stimulus; the theory stated that we could shape behaviour by associating it to a link.
Operant conditioning: B.F. Skinner (1974) used a rat in a box to illustrate how behaviour is influenced by the consequences of our actions. Actions are either rewarded or punished.
Social Learning Theory: Bandura 1973 this illustrated a situation whereby a child learns an anti-social behavior by observing and copying from people they look on to like their parents, teachers or celebrities. Minerka et al (1984) supported this theory by the study of monkeys, he realized that little monkeys developed phobia/fear for snakes after observing their parents having phobia for snakes.
The two strengths of the model are:

It is widely regarded as lending itself to scientific study and evaluation.
It has led to the development of specific behavioral therapies, many of which have had high success rates.

The two weaknesses include:

Environmental causes of abnormal behaviours are only rarely discovered in patient and only symptoms treated not the cause.
The model provides a limited view of the cause of mental illness and does not explain the evidence relating to genetic predispositions to mental illness.

There are many different models used to explain the nature and treatment of mental illness compound and the problems of defining and classifying abnormal behaviour. One of the models is the:
Biological (medical) model
A model is a sort of simplified theory, it consist of a small number of concepts or ideas that are used to provide an outline explanation of a psychological process.
The main emphasis of biological model is that the abnormality is seen as the results of a biological malfunction. This is because the brain is not working properly the person may have abnormal experiences and behave abnormal ways. The underlying assumption of this model is that mental illnesses resemble physical illnesses and can therefore be diagnosed and treated in a similar way.
As an example: A patient presenting with symptoms of depression e.g. extreme tiredness , difficulty in sleeping , lack of interest in life would be diagnosed as having a problem resulting from an in balance of brain chemicals. This problem could be corrected by prescribing drugs to restore the balance.
The limitations of the biomedical model:

There is a difference between physical and mental illness, the diagnosis of physical illness can normally relate to the cause of the problems as an example measuring blood sugar levels could check a diagnosis of diabetes. However as we will see, the cause of many mental illnesses are unknown. This has important consequences for treatments based on the biomedical model, as they can be criticized as focusing only on the symptoms of mental disorders and not the causes.
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.

The strengths of the biological model are:

The model is based on well established sciences such as medicine. It also provides the structured and logical system of diagnosis and treatment.
There is evidence progress that has been made in understanding the biological basis of many mental disorders especially schizophrenia.

References
Class handouts
www.psychologistworld.com
as-psychology.pbworks.com/abnormality Models? Mode
Psychology for AS- Level. M.Cadwell, L clark and C Meldrum