Overview
Depression is one of the most common psychiatric disorders. Symptoms include sad mood and disinterest, as well as physiological and cognitive changes. Sometimes, depression may resemble symptoms of dementia. Therefore, a thorough neuropsychological assessment is useful for some cases to disentangle these potential clinical issues. Depression treatment is commonly done with medications and psychotherapy in the current medical world. Other methods include neurofeedback, transcranial magnetic stimulation, and electroconvulsive therapy.
Typology
Major depressive disorder (MDD) is characterized by episodes of deep depression (occurring for most of the day for at least two weeks) that interferes with everyday functioning. A less severe depressive disorder is persistent depressive disorder (also termed dysthymia), which is a low-grade depression occurring over the course of at least two years that does not substantially interfere with everyday activities (1). In many cases, depression is at least partially reactionary to external stressors. However, there is a small fraction of cases in which depressive symptoms stem solely from brain abnormalities. Therefore, sometimes it is advised to get a neurological workup, or to get a QEEG to determine if brain problems might be the underlying cause.
Symptoms
Symptoms of depression include sadness, disinterest in previously enjoyable activities, unintentional weight loss or gain, sleeping too little or too much, feeing agitated or slowed movements, fatigue or lack of energy, feelings of worthlessness or excessive guilt, and suicidal thoughts (1).
Depression is also associated with cognitive dysfunction, including problems with attention, processing speed, memory, and executive functions (higher-order abilities such as cognitive flexibility and problem-solving). Some individuals with depression may have difficulties with visuospatial processing and left-sided motor abilities (2).
Onset of depression in late-life may present as pseudodementia; therefore, it is important to distinguish between depression and dementia with a comprehensive neuropsychological assessment if there is an onset after the age of 60. In general, compared to individuals with dementia, individuals with depression are slower, are able to retrieve information when given cues (e.g., providing multiple choice), and have less severe cognitive impairment. However, depression may yield a similar clinical picture as certain types of dementia, such as vascular dementia. In fact, some researchers have found links between depression and vascular lesions in brain areas responsible for emotional regulation and cognition, which may suggest a connection between these conditions (3).
Neuroimaging
Depression is associated with the frontal lobe and limbic system of the brain. The former is involved with emotional regulation, while the latter is tasked with emotional processing. Specifically, the amygdala, the anterior cingulate cortex (ACC), and the dorsolateral prefrontal cortex (DLPFC) have been most researched. The amygdala assigns emotional significance to events and helps to retrieve emotionally charged memories. The ventral (or bottom) part of the ACC affects one’s emotional reactions to stimuli. The DLPFC regulates emotions (4). Moreover, the right hemisphere is also implicated in depression, as it has been found to mediate some aspects of emotional processing, such as emotion recognition (2).
Prevalence
Major depressive disorder is the fourth leading cause of disability. Every year, three to five people per 1,000 are diagnosed with major depressive disorder, and the lifetime prevalence is between 5% and 20% of the population. Women are twice as likely to receive the diagnosis relative to men (3).
Course
While persistent depressive disorder is characterized by a relatively stable course, major depressive disorder is episodic. A major depressive episode can partially or completely remit after treatment. However, there is always a risk of recurrence.
Treatments
Depression is mainly treated with antidepressant medications and/or psychotherapy. Studies have found that a combination of the two is most effective (5). An alternative depression treatment technique is electroencephalography (EEG) biofeedback or neurofeedback, which trains the brain to regulate circuits that are involved in depression (6,7).
For a more extensive bibliography of neurofeedback as a treatment for depression, click here.
For individuals with treatment-resistant depression, transcranial magnetic stimulation (TMS) and electroconvulsive therapy (ECT) may be used.
— M. Chen, S. Jacob & J.L. Thomas
References
- American Psychiatric Association (2013). Diagnostic and statistical manual of mental disorders (DSM-5). American Psychiatric Pub.
- Liotti, M, & Mayberg, H (2001). The role of functional neuroimaging in the neuropsychology of depression. Journal of Clinical and Experimental Neuropsychology, 23(1), 121-136.
- McClintock, S, Husain, M, Greer, T, & Cullum, C (2010). Association between depression severity and neurocognitive function in major depressive disorder: A review and synthesis. Neuropsychology, 24(1), 9-34.
- Gotlib, I, & Hamilton, J (2008). Neuroimaging and depression: Current status and unresolved issues. Current Directions in Psychological Science, 17(2), 159-163.
- Pampallona, S, Bollini, P, Tibaldi, G, Kupelnick, B, & Munizza, C (2004). Combined pharmacotherapy and psychological treatment for depression: A systematic review. Archives of General Psychiatry, 61(7), 714-719.
- Linden, D (2014). Neurofeedback and networks of depression. Dialogues in Clinical Neuroscience, 16(1), 103-112.
- Hammond, D (2005). Neurofeedback treatment of depression and anxiety. Journal of Adult Development, 12(2-3), 131-137.