Why Do Antidepressants Cause Side effects?

Antidepressants cause various side effects like: dry mouth, headache, restlessness and sexual dysfunction. This happens because the brain and body measures the rising level of hormones, which happens when we take antidepressants, and body tries to adjust with the changes. 
 

Antidepressants works by changing the levels of neurotransmitters such as serotonin, dopamine, and norepinephrine in the brain which is important for maintaining mood. 
 

When you start taking antidepressants they can Initially make you feel worse sometimes because they activate a part of your brain that increases a stress hormone, called corticotropin releasing factor. 
 

This factor can cause restlessness, which goes away in few days or weeks. 
 

Antidepressants can cause decreased sodium levels in blood which causes confusion, headache, and nausea. 
 

When serotonin interacts with other medicines, it can cause serotonin levels become too high in brain leading to a condition called serotonin syndrome. Symptoms of serotonin syndrome are: confusion, anxiety, stiff muscles and sweating. 
 

Antidepressants may also interfere with levels of chemicals like acetylcholine in the brain and other organs which can lead to blurred vision, confusion, constipation, burning urination, drowsiness, dry mouth, increased eye pressure and increased blood pressure. 
 

Source1:-Jiang, Y., Peng, T., Gaur, U., Silva, M., Little, P., Chen, Z., ... & Zheng, W. (2019). Role of corticotropin releasing factor in the neuroimmune mechanisms of depression: examination of current pharmaceutical and herbal therapies. Frontiers in cellular neuroscience, 13, 290. https://www.frontiersin.org/journals/cellular-neuroscience/articles/10.3389/fncel.2019.00290/full
 

Source2:-Arborelius L, Owens MJ, Plotsky PM, Nemeroff CB. The role of corticotropin-releasing factor in depression and anxiety disorders. J Endocrinol. 1999 Jan;160(1):1-12. doi: 10.1677/joe.0.1600001. PMID: 9854171. https://pubmed.ncbi.nlm.nih.gov/9854171/