Clinical depression is a debilitating psychiatric disorder characterized by low mood, associated with alterations in behavior, activity level and thinking. It can become chronic or recurrent, significantly impairing the ability to cope with daily life. It affects more than 350 million people worldwide and is the world's leading cause of disability.

The exact causes of depression are unknown, although, as with other mental disorders, various factors such as physical changes in the brain, alterations in neurotransmitter levels and/or changes in hormonal balance (e.g., pregnancy and postpartum) may occur.

In addition to the above, there are a number of risk factors that may favor the triggering of depression. Among them:

  • Age: it is more frequent in adults, although it can appear at any time of life.
  • It is more common in women.
  • Having low self-esteem or being overly dependent can increase susceptibility to depression.
  • Traumatic or stressful situations, such as the loss of a loved one or financial problems.
  • Family history of other mental illnesses such as bipolar disorder, alcoholism or suicide.
  • History of other disorders such as anxiety or eating disorders.
  • Alcohol and drug abuse.
  • Other illnesses such as cancer or those with chronic pain.
  • Certain medications.

Although it is known that there is a genetic component in the development of the pathology, the heritability of the disease is not clear. Among the GWAS studies carried out, there is one that includes some 250,000 cases and more than 50,500 controls in which 96 susceptibility loci were identified. Among the loci identified, those associated with synaptic structure and neurotransmission, such as DRD2, which codes for the dopamine D2 receptor, stand out. This study also highlights the correlation between depression and other disorders such as schizophrenia. It is therefore very useful in trying to understand the genetic architecture of depression and provide new avenues for future research.


Depression may occur once in a lifetime or recur on a recurring basis. During this period, symptoms may include:

  • Feelings of sadness or despondency, tearfulness or hopelessness.
  • Mood swings and irritability.
  • Loss of interest in most usual activities.
  • Sleep disturbances.
  • Tiredness and lack of energy.
  • Lack of appetite and weight loss.
  • Slowness to speak, to reason or to move.
  • Feeling of guilt.
  • Difficulty concentrating.
  • Negative thoughts that may include suicidal thoughts.


Prevention programs have been shown to reduce the risk of depression. Among community strategies, school programs to promote a positive coping model among children, interventions aimed at parents of children with behavioral problems or exercise programs for the elderly stand out.

In addition, there are other strategies that may be helpful:

  • Avoid stress.
  • Lean on family and friends to get you through times of crisis.
  • Seek treatment at the first signs of a problem (especially psychological).
  • Undergo long-term supportive treatment to prevent the recurrence of symptoms in cases of recurrent depression.

Number of observed variants

13.5 million variants

Number of risk loci analyzed in the study

96 loci


Howard DM, Adams MJ, Clarke TK, et al. Genome-wide meta-analysis of depression identifies 102 independent variants and highlights the importance of the prefrontal brain regions. Nature Neuroscience. 2019 Mar;22(3):343-352.

Mayo Clinic [March 2022]

World Health Organization (WHO) [March 2022]

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