Depression is a serious affective disorder that affects millions of people in the world, approximately 5% of the population. In the United States alone approximately 33 million people will suffer from depression at some point in their life (Bear, 2007). In addition, the disorder is the leading cause of suicide. Despite its high prevalence, however, stigma still also remains high. A primary reason for the stigma surrounding any mental disorder is a misunderstanding of the symptoms and causes.
Even though depression strikes people differently, the cardinal symptoms are lowered mood and feelings of dejection, a lack of pleasure or interest rather than sadness. Accompanying symptoms include changes in appetite, fatigue, insomnia or hypersomnia, diminished concentration, feelings of worthlessness and/or guilt and recurrent thoughts of death and/or suicide (Bear, 2007). Depression can be one half of bipolar disorder but also occur on its own and in varying degrees of severity. Usually, for a diagnosis of major depression, the cardinal symptoms of depression must be present every day for approximately 2 weeks. Importantly, the cause of depression cannot be linked to a bereavement. This clear distinction is what separates depression from sadness.
Types of depression include chronic depression of dysthymia, major or clinical depression, atypical depression and manic depression. Chronic depression or dysthymia is usually less severe than major or clinical depression; however, it can be more disabling in that the symptoms are long-term (2 years+) or recurrent throughout a lifetime. Major or clinical depression is more severe; however, the symptoms do not last longer than 2 years and is not typically recurrent. Approximately 17% of sufferers have chronic symptoms. It is important to note, however, that when depression is left untreated, recurrence is far more likely. Manic depression is found in bipolar disorder, to find out more click here. Finally, atypical depression is when a person suffers from the accompanying symptoms rather than the cardinal symptoms.
Aetiology and Treatment Options
Affective or mood disorders such as depression alter the typical function of the brain. Many different parts of the brain are usually affected at the same time, but the major system involved is the hypothalamic-pituitary-adrenal system (HPA). Exaggerated activity in the HPA system is common in people with anxiety and affective disorders. Specific to depression, blood cortisol levels are heightened as is the concentration of corticotropin-releasing hormones (CRH) in the cerebrospinal fluid.
The monoamine hypothesis of depression states that a deficit in monoamines causes mood disorders. Monoamines include serotonin and catecholamines (inc. dopamine, noradrenaline, norepinephrine). Current anti-depressants focus on this theory of depression. Anti-depressants inhibit the re-uptake of of monoamines, increasing the concentration of them in the synaptic cleft. The great benefit of anti-depressants is that they promote long-term, adaptive changes in the brain reducing the possibility of another depressive episode. Unfortunately, not all depressed people find anti-depressants effective. This can mean that either the treatment does not work for them at all or they require a greater dosage. Furthermore, it can takes week for depressants to take affect. Lastly, anti-depressants can raise levels of norepinephrine, which makes anti-depressants less effective. As anti-depressants are not always effective, patients with prolonged depressive episodes may seek alternative treatment. Electroconvulsive therapy (ECT) and therapy are both options. ECT is mainly used in extreme cases because it can offer immediate relief. However, ECT is controversial due to the danger of memory loss. This is not surprising considering ECT is a localised seizure controlled by keeping the patient under anaesthesia. It is unknown exactly how ECT works; however, the hippocampus has been implicated. The hippocampus is involved in regulating CRH levels and the HPA system.
Types of anti-depressants include: selective serotonin re-uptake inhibitors, serotonin-noradrenaline re-uptake inhibitors, tricyclic anti-depressants and monoamine oxidase inhibitors. For people with bipolar disorder, lithium is also used to stabilise mood primarily the mania but has been shown stabilise mood overall.
The diathesis-stress hypothesis proposes that mental disorders have a genetic component that predisposes us to mental illness. Certain life stressors then makes us susceptible to mental illness actually presenting themselves. As such, traumatic childhoods full of abuse and/or neglect can leave a child at high risk for developing mental disorders. Tragically, children whose poor treatment is due to mentally ill caregivers, this cycle becomes hard to break. However, according to the diathesis-stress model, a trigger is not enough to bring forth mental illness without a genetic foundation. This genetic foundation goes hand in hand with the HPA system. Of course this does not mean that only traumatised children will suffer from mental health disorders. Individuals that have experienced a highly stressful life even such as divorce, moving away from home, changing schools, becoming ill, etc. will also be at risk are they predisposed to mental health issues.
In a healthy individual, cortisol activates hippocampal glucocorticoid receptors, which inhibit the the HPA system. However, in a depressed individual there is a flaw in the feedback system. On a molecular level there is a diminished hippocampal response to cortisol due to reduced number of glucocorticoid receptors. Here the genetic component of depression comes into play; glucocorticoid receptors are the product of gene expression. Hence, an individual with few glucocorticoid receptors is more susceptible. Fittingly, the amount of glucocorticoid receptors are epigentically influenced, early sensory experience can alter the number as well. This means that a childhood where we are well looked after, loved, cared for, kept safe and happy can protect us from developing depression even if we disposed to at birth. This illustrates how important the interaction of nature and nurture is. Think Voldemort vs Harry Potter. Despite the traumatic death of his parents, the one year of unconditional love and Lily’s sacrifice protected him not just magically but neurologically. Interestingly, in an interview with Oprah Winfrey, JK Rowling discuss this exact point.
Antidepressants . (n.d.). Antidepressants. Retrieved July 18, 2014, from http://www.nhs.uk/conditions/Antidepressant-drugs/Pages/Introduction.aspx
Bear, M. F., Connors, B. W., & Paradiso, M. A. (Eds.). (2007). Neuroscience(Vol. 2). Lippincott Williams & Wilkins.
Pinel, J. P. (2010). Biopsychology (8th ed., International ed.). Harlow: Pearson Education.
What the Heck is an HPA Axis & What Does it Have to do with Stress?. (n.d.).Fibromyalgia & Chronic Fatigue. Retrieved July 18, 2014, from http://chronicfatigue.about.com/od/cfsglossary/g/hpa_axis.htm