Depression is a mental health disorder characterized by feelings of sadness, despair, low self-esteem, loss of interest in daily activities, and suicidal thoughts. People with depression experience negative emotions toward others and themselves.
Unlike sadness (which is a temporary emotion that manifests in a low mood), the typical symptoms of depression last at least two weeks.
Depression is one of the most common mental illnesses worldwide, but the rate of people with depression varies from country to country. 4.4% of the global population suffers from depression. In the US, around 5.9% of the population has depression.
In addition, the global rate of depression is twice as high among women than it is among men.
Recent studies have shown that the prevalence of this disorder has increased significantly in the last few decades. It is estimated that 16% of the world’s population will suffer from depression during their lifetime.
What are the symptoms?
To be diagnosed with depression, most or some of the following symptoms must be present for at least two weeks.
Physical symptoms: significantly reduced or increased appetite, sleep disturbances, weight gain or loss, fatigue, constipation or diarrhea, vision impairments, aversion to noise, and aversion to physical contact.
Emotional symptoms: feelings of emptiness, helplessness, worthlessness, hopelessness, decreased libido, hatred and self-criticism, social withdrawal, despair, sadness, distress, irritability, anger, loss of energy.
Cognitive symptoms: decreased ability to concentrate, impaired memory, difficulties in long-term planning, difficulties in understanding the broad context of events, low self-esteem, a pessimistic outlook on life.
Neurological symptoms: Enlarged amygdala, reduced hippocampal volume, MPFC overactivity and MTL underactivity.
Depression and genetics
Despite unprecedented advancements in molecular biology, the gene mutations that are associated with depression have not yet been discovered. However, there is no doubt that a certain link exists between depression and heredity.
Although several genetic phenomena that are common to many patients have been discovered, these phenomena do not explain the existence of the disease in the entire patient population.
In 2003, a group of researchers reported that they have successfully identified a specific gene, called DEP1, in common to many patients in a study carried out among 400 families with a long family history of depression. In 2010, researchers from Yale University found an increased presence of the gene MKP-1 in the postmortem brain examinations of twenty-one patients.
However, it seems that the day researchers will be able to clearly identify the genetic basis of depression is still far away. Accordingly, there currently is no prenatal screening test that can diagnose if a fetus is at an increased risk for depression, nor is there preconception testing that can help parents-to-be understand their risk for passing on depression to their child.