Related Posts:

OpenStax Biology 2e

Major depression affects approximately 6.7 percent of the adults in the United States each year and is one of the most common mental disorders. To be diagnosed with major depressive disorder, a person must have experienced a severely depressed mood lasting longer than two weeks along with other symptoms including a loss of enjoyment in activities that were previously enjoyed, changes in appetite and sleep schedules, difficulty concentrating, feelings of worthlessness, and suicidal thoughts. The exact causes of major depression are unknown and likely include both genetic and environmental risk factors. Some research supports the “classic monoamine hypothesis,” which suggests that depression is caused by a decrease in norepinephrine and serotonin neurotransmission. One argument against this hypothesis is the fact that some antidepressant medications cause an increase in norepinephrine and serotonin release within a few hours of beginning treatment—but clinical results of these medications are not seen until weeks later. This has led to alternative hypotheses: for example, dopamine may also be decreased in depressed patients, or it may actually be an increase in norepinephrine and serotonin that causes the disease, and antidepressants force a feedback loop that decreases this release. Treatments for depression include psychotherapy, electroconvulsive therapy, deep-brain stimulation, and prescription medications. There are several classes of antidepressant medications that work through different mechanisms. For example, monoamine oxidase inhibitors (MAO inhibitors) block the enzyme that degrades many neurotransmitters (including dopamine, serotonin, norepinephrine), resulting in increased neurotransmitter in the synaptic cleft. Selective serotonin reuptake inhibitors (SSRIs) block the reuptake of serotonin into the presynaptic neuron. This blockage results in an increase in serotonin in the synaptic cleft. Other types of drugs such as norepinephrine-dopamine reuptake inhibitors and norepinephrine-serotonin reuptake inhibitors are also used to treat depression.


Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at:

Keywords: what is depression, meaning of depression, define depression, depression in United States, diagnosing depression, symptoms of depression, signs of depression, medication of depression, cure for depression, depression treatment, causes of depression, effects of depression, biology of depression, depression

Research Article: Conceptual Challenges of a Tentative Model of Stress-Induced Depression

Date Published: January 30, 2009 Publisher: Public Library of Science Author(s): Bernhard Baune, Peter Binfield. Abstract: None Partial Text: The concept of a stress-induced depression has recently been proposed in light of new findings from animal and human studies. Depression associated with stress involves a number of body systems such as the neuroendocrine and neurotransmitter … Continue reading

Research Article: Helpful Factors in the Treatment of Depression from the Patient’s, Carer’s and Professional’s Perspective: A Concept Map Study

Date Published: December 16, 2016 Publisher: Public Library of Science Author(s): Rosa A. van Grieken, Hanka F. Verburg, Maarten W. J. Koeter, Jessica Stricker, Udo W. Nabitz, Aart H. Schene, Pietro Cipresso. Abstract: Depression research has resulted in knowledge about neurobiology, pharmacological strategies and short-term cost-effective treatments. However, more than two-thirds of all depressed … Continue reading

Research Article: Expression Profiling of a Genetic Animal Model of Depression Reveals Novel Molecular Pathways Underlying Depressive-Like Behaviours

Date Published: September 7, 2010 Publisher: Public Library of Science Author(s): Ekaterini Blaveri, Fiona Kelly, Alessandra Mallei, Kriss Harris, Adam Taylor, Juliet Reid, Maria Razzoli, Lucia Carboni, Chiara Piubelli, Laura Musazzi, Girogio Racagni, Aleksander Mathé, Maurizio Popoli, Enrico Domenici, Stewart Bates, Hiromu Tanimoto. Abstract: The Flinders model is a validated genetic rat model of depression … Continue reading

Research Article: CRY2 Is Associated with Depression

Date Published: February 24, 2010 Publisher: Public Library of Science Author(s): Catharina Lavebratt, Louise K. Sjöholm, Pia Soronen, Tiina Paunio, Marquis P. Vawter, William E. Bunney, Rolf Adolfsson, Yvonne Forsell, Joseph C. Wu, John R. Kelsoe, Timo Partonen, Martin Schalling, Andreas Reif. Abstract: Abnormalities in the circadian clockwork often characterize patients with major depressive and … Continue reading

Research Article: Predicting Outcome in Internet-Based Cognitive Behaviour Therapy for Major Depression: A Large Cohort Study of Adult Patients in Routine Psychiatric Care

Date Published: September 12, 2016 Publisher: Public Library of Science Author(s): Samir El Alaoui, Brjánn Ljótsson, Erik Hedman, Cecilia Svanborg, Viktor Kaldo, Nils Lindefors, Emilio Russo. Abstract: Although the effectiveness of therapist-guided internet-based cognitive behaviour therapy (ICBT) for treating depression has been well documented, knowledge of outcome predictors and risk factors associated with lower … Continue reading

Research Article: Modeling the Dynamics of Disease States in Depression

Date Published: October 17, 2014 Publisher: Public Library of Science Author(s): Selver Demic, Sen Cheng, H. Sunny Sun. Abstract: Major depressive disorder (MDD) is a common and costly disorder associated with considerable morbidity, disability, and risk for suicide. The disorder is clinically and etiologically heterogeneous. Despite intense research efforts, the response rates of antidepressant … Continue reading

Research Article: Depression-Burnout Overlap in Physicians

Date Published: March 1, 2016 Publisher: Public Library of Science Author(s): Walter Wurm, Katrin Vogel, Anna Holl, Christoph Ebner, Dietmar Bayer, Sabrina Mörkl, Istvan-Szilard Szilagyi, Erich Hotter, Hans-Peter Kapfhammer, Peter Hofmann, Jacobus van Wouwe. Abstract: Whether burnout is a distinct phenomenon rather than a type of depression and whether it is a syndrome, limited … Continue reading

Research Article: Goal Fluency, Pessimism and Disengagement in Depression

Date Published: November 30, 2016 Publisher: Public Library of Science Author(s): Joanne M. Dickson, Nicholas J. Moberly, Christian O’Dea, Matt Field, Nico W. Van Yperen. Abstract: Despite the development of prominent theoretical models of goal motivation and its importance in daily life, research has rarely examined goal dysregulation processes in clinical depression. Here we … Continue reading

Research Article: Impact of depression on speech perception in noise

Date Published: August 15, 2019 Publisher: Public Library of Science Author(s): Zilong Xie, Benjamin D. Zinszer, Meredith Riggs, Christopher G. Beevers, Bharath Chandrasekaran, Shane Lindsay. Abstract: Effective speech communication is critical to everyday quality of life and social well-being. In addition to the well-studied deficits in cognitive and motor function, depression also impacts communication. … Continue reading

Research Article: Major Depression as a Complex Dynamic System

Date Published: December 8, 2016 Publisher: Public Library of Science Author(s): Angélique O. J. Cramer, Claudia D. van Borkulo, Erik J. Giltay, Han L. J. van der Maas, Kenneth S. Kendler, Marten Scheffer, Denny Borsboom, Igor Branchi. Abstract: In this paper, we characterize major depression (MD) as a complex dynamic system in which symptoms … Continue reading