Depression is a type of disease with a biological basis influenced by genetic factors, and the occurrence of depression is also influenced by social, psychological and cultural factors. This forms a unified biopsychosocial model, which is the result of the combined action of many factors.
1.Genetics
Epidemiological surveys show that the chance of depression among relatives of depressed patients is 10-30 times higher than that of the general group, and the closer the blood relationship, the higher the chance of the disease. Molecular genetic studies have revealed that the frequency of the T102C polymorphic allele A2 of the 5-HT2a receptor gene predominates in depressed patients. Depression has been found to be significantly associated with human genetic factors, but is not an inherited disorder. It is generally believed that genetic factors in the occurrence of depression may lead to a susceptible quality.
2.Biochemical factors
(1) Abnormal metabolism of monoamine neurotransmitters: the biogenic amines norepinephrine (NE) and 5-hydroxytryptamine (5-HT) are two neurotransmitters closely related to the pathophysiology of depression. Numerous studies have shown that depression may be due to hypofunction of the NEergic system alone or the 5-HTergic system alone, and that dopamine (DA) plays an equally important role in depression. Recently, the peptide neurotransmitter DD growth inhibitor (SS) has become a new hot spot in the study of the pathogenesis of depression.
(2) Altered receptor function
(3) Neuroendocrine disorders.
(1) HPA axis abnormalities: including hypercortisolemia with altered circadian secretion rhythm; dexamethasone deregulation in about half of depressed patients; increased adrenal gland volume; enhanced glucocorticoid secretion caused by adrenocorticotropic hormone (ACTH); high levels of adrenaline-releasing hormone in cerebrospinal fluid; and sluggish response of ACTH secretion to exogenous CRH. In general, the more severe the depression and the older the age, the more pronounced the HPA axis abnormalities.
(ii) HPT axis abnormalities: depressed patients may show loss or flattening of the circadian rhythm of thyroid hormone secretion.
(iii) Abnormal growth hormone secretion: Under normal circumstances, there is a circadian rhythm of growth hormone (GH) secretion, which peaks during slow eye movement sleep, but this peak flattens in depressed patients.
3.Socio-cultural and psycho-social factors
Socio-cultural factors refer to the role of social system, economic status, social living conditions, cultural environment, and medical equality in the process of disease occurrence. Stressful life events, such events can produce persistent changes in the patient leading to physiological brain activity, such persistent changes may alter the functional state of some neurotransmitter systems as well as intracellular messenger systems, and there may also be organizational changes such as loss of neurons and reduction of synaptosomes.
4. Personality factors,
Personality quality research found that patients often have personality defects,
Such as depression, reticence, dependence, low self-esteem, lack of cheerfulness, timid and fearful, and tendency to be anxious and pessimistic. Their personality deficits often lead to cognitive distortions, with learned negative thought patterns,
This leads to depressive feelings in patients.
5. Changes in biological rhythms
Depression is often accompanied by sleep disturbances and circadian mood changes, revealing that synchronization disorders of circadian rhythms may cause depression.
6.Sleep and brain electrophysiology
Existing studies have found that the mean amplitude of the principal components of the somatosensory evoked response to any fixed intensity stimulus is higher in major depressive disorder, which is significantly different from neurotic depression, schizophrenia and normal individuals. Moreover, the evoked potential recovery function was significantly lower in depressed patients and improved to the normal range upon recovery from the disease. It has also been demonstrated that reduced visual evoked potential amplitude in both hemispheres of depressed patients is significantly negatively correlated with clinical scale scores. Many scholars are currently studying the analysis of cognitive-related potentials, especially P300 and N400, but no valuable reports have been seen.
(II) Progress of antidepressant drugs
In the past 20 years, the research of drugs for depression has been innovated [19]. In the past, the only two major classes of antidepressants were monoamine oxidase inhibitors (MAOI) and tricyclic antidepressants (TCA). Due to the development of psychotropic drugs, some new atypical antidepressants with different chemical structures and pharmacological effects from the classical tricyclics have been introduced, such as selective 5-HT reuptake inhibitors (SSRI), selective norepinephrine reuptake inhibitors (NRI) and 5-HT
and norepinephrine reuptake inhibitors (SNRI), etc. These drugs have provided new and more options for the treatment of depression.