Antidepressant medication is a primary biological treatment for unipolar depression, with selective serotonin reuptake inhibitors (SSRIs) being among the most commonly prescribed. These drugs work by blocking the reabsorption of serotonin in the brain, allowing more of this neurotransmitter to remain available in the synaptic space between neurons. This mechanism addresses the hypothesized serotonin deficiency thought to underlie depressive symptoms. Other antidepressant classes include serotonin-norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants, and monoamine oxidase inhibitors (MAOIs), each targeting different neurotransmitter systems [1][2].

Antidepressants are typically considered first-line treatment for moderate to severe depression and may also be used for mild cases depending on symptom severity and patient preference. A key advantage is their relatively rapid action compared to psychotherapy alone, which is particularly important for severely depressed individuals or those at risk of self-harm. However, these medications are not immediate solutions; they usually require several weeks of consistent use before patients notice meaningful symptom improvement. Common side effects include nausea, sleep disturbance, sexual dysfunction, weight changes, and agitation. Treatment is individualized, as different patients respond better to specific medications or dosages [1][2].

For treatment-resistant cases where initial antidepressants prove ineffective, clinicians may adjust doses, switch medications, or employ augmentation strategies such as lithium [3]. While antidepressants address the chemical imbalances underlying depression, they are often most effective when combined with psychological therapies, allowing patients to engage more fully in behavioral and cognitive work. Overall, pharmacological intervention remains a cornerstone of biological treatment for unipolar depression.