All human (and animal) behavior is a product of biological structures and processes, highly organized on multiple interconnected levels. The nervous system is highly specialized and hierarchical in its structure, but neuroplasticity gives the brain some flexibility to adapt its structure and function.

Biological factors are microorganisms (bacteria, viruses, fungi and microscopic parasites), cell cultures, human endoparasites and components from microorganisms that can cause damage to health in humans.

The biological perspective is a way of looking at psychological issues by studying the physical basis for animal and human behavior. It is one of the major perspectives in psychology and involves such things as studying the brain, immune system, nervous system, and genetics.

Biological psychology is concerned primarily with the relationship between psychological processes and the underlying physiological events—or, in other words, the mind-body phenomenon.

The practical applications of biological psychology include discovering disease processes, as well as gaining a better understanding of healthy…

The biological approach believes behavior to be as a consequence of our genetics and physiology. It is the only approach in psychology that examines thoughts, feelings, and behaviors from a biological and thus physical point of view.

Key assumptions of the biological approach:

• There is a direct correlation between brain activity and cognition.
• Biochemical imbalances can affect behaviour.
• Brain physiology can affect behaviour.
• Behaviour can be inherited (as it is determined by genetic information)

“Everything psychological is simultaneously biological”- meaning of the phrase? It means that everything that happens in our mind is the result of a biological event- a series of nerve impulses. It is a nerve cell; the basic building block of the nervous system.

The main biological explanations of depression are as follows: Genetic – there is considerable evidence that the predisposition to develop depression is inherited. Biochemistry, e.g. Amine hypothesis – low levels of mono amines predominantly noradrenaline and serotonin.

Behavioral theory posits that certain environmental changes and avoidant behaviors inhibit individuals from experiencing environmental reward and reinforcement and subsequently leads to the development and maintenance of depressive symptoms.

The DSM and ICD serve as guides for the diagnosis of mental disorders. These two approaches use a category-based classification system, meaning specific conditions are grouped within broader categories of disorder.

The drugs are divided in three groups: the classical tricyclic antidepressants, the MAO inhibitors and the recent antidepressants. Some drugs with potential antidepressant properties are also studied. The other biological treatments of depression include electroconvulsive therapy and sleep deprivation.

The most common types of mood disorders are major depression, dysthymia (dysthymic disorder), bipolar disorder, mood disorder due to a general medical condition, and substance-induced mood disorder. There is no clear cause of mood disorders.