Depression and genetics
Depression is a complex mental health condition characterized by persistent feelings of sadness, hopelessness, and a loss of interest in daily activities. It affects individuals across all age groups and can manifest in various symptoms, ranging from emotional distress to physical complaints. Genetics plays a significant role in the risk of developing major depressive disorder, with studies indicating a familial tendency toward the condition. Research involving twins suggests that the likelihood of both identical twins experiencing depression is considerably higher than in fraternal twins, highlighting the genetic component.
Several genes, including those associated with serotonin production and transport, have been linked to depression, although the exact inheritance patterns remain unclear. Environmental factors, such as stressful life events and lack of social support, also contribute to the disorder. Treatment options for depression often combine medication and psychotherapy, with various classes of antidepressants available, though they may come with side effects. Additionally, lifestyle changes, such as regular exercise and social support, can aid in prevention and management. Understanding both genetic and environmental influences is crucial for addressing depression effectively and compassionately.
Depression and genetics
DEFINITION Depression is a mental illness marked by feelings of profound sadness and lack of interest in activities. Depression is not the same as a blue mood. It is a persistent low mood that interferes with the ability to function and appreciate things in life. It may cause a wide range of symptoms, both physical and emotional. It can last for weeks, months, or years. People with depression rarely recover without treatment.
ALSO KNOWN AS: Major depressive affective disorder; unipolar disorder; unipolar mood disorder
Risk Factors
Females and the elderly are at risk for depression. Other risk factors include chronic physical or mental illness, including thyroid disease, headaches, chronic pain, and stroke; a previous episode of depression; major life changes or stressful life events, such as bereavement or trauma; postpartum depression; the winter season for seasonal affective disorder; little or no social support; low self-esteem; and lack of personal control over an individual’s circumstances. Additional risk factors are a family history of depression (parent or sibling); feelings of helplessness; using certain medications, including medications used to treat asthma, high blood pressure, arthritis, high cholesterol, and heart problems; smoking; anxiety; insomnia; personality disorders; and hypothyroidism.
Etiology and Genetics
Major depressive disorder is a condition in which multiple environmental and genetic factors play a contributing part. Some individuals are genetically predisposed to develop the condition, yet a detailed genetic analysis and prediction of inheritance patterns are not possible, since so many different genes seem to be implicated. It has been known for decades that depression tends to run in some families, and twin studies have confirmed that genetics plays a critical role. One study reports that in fraternal twins (who share approximately 50 percent of the same genes), if one twin develops depression the other will also be diagnosed with the condition about 20 percent of the time. In identical twins (who share 100 percent of the same genes), however, the rate of concordant diagnoses of depression rises to 76 percent.
Molecular genetics studies conducted during and since the completion of the Human Genome Project have identified several genes that likely play a role in the predisposition for or development of depression. There is considerable disagreement among the researchers, however, so the candidate genes in the following list must be considered as only possible contributing factors. The TPH1 gene, located on the short arm of chromosome 11 (at position 11p15.3-p14) encodes the enzyme tryptophan hydroxylase 1, which is important for the synthesis of serotonin (a neurotransmitter produced in the brain that may affect mood). The SLC6A4 gene on the long arm of chromosome 17 (at position 17q11.1-q12) specifies the serotonin transporter protein, and the gene 5HTR2A (at position 13q14-q21) codes for the serotonin 2A receptor protein. The COMT gene on chromosome 22 (at position 22q11.2) encodes the enzyme catechol-o-methyltransferase, which is important for the metabolism of dopamine (another brain neurotransmitter). Finally, the gene BDNF (at position 11p13), which specifies the brain-derived neurotrophic factor, may be involved in the etiology of several different neuropsychiatric behaviors. In 2015, University of Oxford geneticists located two markers associated with depression, one that is adjacent to the SIRT1 gene.
Symptoms
Depression can differ from person to person. Some people have only a few symptoms, while others have many. Symptoms can change over time and may include persistent feelings of sadness, anxiety, or emptiness; hopelessness; feelings of guilt, worthlessness, or helplessness; loss of interest in hobbies and activities; loss of interest in sex; tiredness; trouble concentrating, remembering, or making decisions; and trouble sleeping, waking up too early, or oversleeping. Other symptoms may include eating more or less than usual; weight gain or weight loss; thoughts of death or suicide, with or without suicide attempts; restlessness or irritability; and physical symptoms that defy standard diagnosis and do not respond well to medical treatments.
Screening and Diagnosis
The doctor will ask about a patient’s symptoms and medical history, giving special attention to alcohol and drug use, thoughts of death or suicide, family members who have or have had depression, sleep patterns, and previous episodes of depression.
The doctor may also perform specific mental health exams; this will help get detailed information about the patient’s speech, thoughts, memory, and mood. A physical exam and other tests can help rule out other causes.
Treatment and Therapy
Treatment may involve the use of medicine, psychotherapy, or both. Severe depression usually requires hospital care and the use of drugs, such as olanzapine.
A vast majority of depressed patients find relief from their symptoms with antidepressant medications, which can take two to six weeks to reach their maximum effectiveness. These medications include selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), citalopram (Celexa), fluvoxamine (Luvox), and escitalopram (Lexapro).
The US Food and Drug Administration advises that people taking antidepressants should be closely observed. For some, the medications have been linked to worsening symptoms and suicidal thoughts. These adverse effects are most common in young adults. These effects tend to occur at the beginning of treatment or when there is an increase or decrease in the dose.
Although the warning is for all antidepressants, of most concern are the SSRI class, such as Prozac, Zoloft, Paxil, Luvox, Celexa, and Lexapro.
Another form of treatment is the use of tricyclic antidepressants, such as imipramine (Tofranil), doxepin (Adapin, Sinequan), clomipramine (Anafranil), nortriptyline (Pamelor), and mitriptyline (Elavil); and the use of monoamine oxidase inhibitors (MAOIs), such as phenelzine (Nardil) and tranylcypromine (Parnate). Other antidepressants include venlafaxine (Effexor), nefazodone (Serzone), mirtazapine (Remeron), bupropion (Wellbutrin), and duloxetine (Cymbalta).
Short-term psychotherapy (ten to twenty weeks) can help some people. Psychotherapy is designed to help patients cope with difficulties in relationships, change negative thinking and behavior patterns, and resolve difficult feelings.
Electroconvulsive therapy (ECT) is the use of an electric stimulus to produce a generalized seizure. It may be used in people with severe or life-threatening depression. ECT is also used for people who cannot take or do not respond to medicine. It is considered a safe and effective procedure.
A regular exercise program has been shown to relieve some of the symptoms of depression. It should play a large role in the overall management of depression. Phototherapy treatment is done by sitting under special lights; it usually lasts about thirty minutes every morning.
St. John’s wort is an herb that is available without prescription. It is widely used in Europe for the treatment of mild to moderate depression. Studies have shown that the herb is as effective as standard antidepressants and has fewer side effects although it can interfere with some medications.
There is also evidence that dehydroepiandrosterone (DHEA), a dietary supplement, may help some people. DHEA is an ingredient in fish oil. Some experts disagree with these findings. Patients always should discuss the use of dietary and herbal supplements with their doctors.
Research suggests that diets high in tryptophan, certain B vitamins, and fish oil may be helpful. They have shown promise in both relieving and preventing depression. Patients should always discuss the use of such supplements with their doctors.
Vagal nerve stimulation (VNS) is used as a therapy for depression when multiple trials of medicine do not work. A pacemaker-like device stimulates the vagus nerve in the neck.
Prevention and Outcomes
Individuals can reduce their chances of becoming depressed by being aware of their personal risks; having psychiatric evaluations and psychotherapy, if needed; developing social supports; learning stress management techniques; exercising regularly; avoiding the abuse of alcohol or drugs; and getting adequate sleep, rest, and recreation.
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