生物学上的抑郁症是基于抑郁症有一个自然原因的概念，一种理论是许多人更倾向于通过他们的基因发展成抑郁症。提示5-HTT基因是突变和遗传的。5-HTT基因负责血清素的产生。家庭、双胞胎和收养的研究都有助于帮助遗传学在抑郁症发展中的作用。Gershon证实，如果一个孩子的父母有抑郁症，那么这个孩子患抑郁症的可能性会增加2-3倍。由Wegner进行的双胞胎研究发现，如果亲生父母也患有抑郁症，孩子患抑郁症的可能性是养父母的8倍。这也表明抑郁症是由基因而不是环境因素造成的。使用双胞胎和家庭研究的一个缺点是，参与这个实验的个体通常仍然共享相同的基因，这可能比共享的基因有更大的影响。大脑中的许多化学物质被用作信使，与身体的其他部分、大脑的不同部分以及神经系统进行交流。这些化学信使被称为神经递质，它们被称为神经元的大脑神经细胞释放和接收。神经元通过交换神经递质而不断地相互沟通。这个交流系统对大脑的正常运作至关重要。大脑中的抑郁与神经递质5 -羟色胺、去甲肾上腺素和多巴胺有关。用来缓解抑郁症状的抗抑郁药物也会作用于这些特定的神经递质及其受体。生物学方法治疗抑郁症的一个优点是它可以是确定性的。原因是治疗行为异常的人是很有可能的。这种解释可以帮助人们过上更好的生活。它的一个缺点是，它没有涵盖痛苦、思想和感觉的经历(tutor2u, n.d.)，也没有把环境因素考虑进去，因为它是一种遗传的抑郁方法。从生物学上来说，不同的强度可以是结果，很容易定量和精确地测量，所以从长远来看，可用的治疗是有效的，并被证明是有效的。
Biologically depression is based on the concept of that there is a natural cause towards depression, one theory would be that many individuals are more inclined to develop depression through their genetics. It is suggested that the 5-HTT gene was mutated and inherited. The 5-HTT gene is responsible for the production of serotonin. Family, twin and adoption studies have all helped to aid the role of the genetics in the advancement of depression. Gershon established that if a parent of a child had depression, that the child was then 2-3 times more likely to suffer from the disorder themselves. Twin studies, conducted by Wegner, found that children are 8 times more likely to develop depression if their biological parent also suffered than if their adoptive parent did. It is also suggesting that depression is widely shaped more by genetics rather than environmental factors. One disadvantage of using twin and family studies would be that the individuals who are taking part in this experiment are usually still sharing the same which could have more of an influence than the shared genes. Many chemicals in the brain are used as messengers to communicate with other parts of the body and different parts of the brain itself and also with the nervous system. These chemical messengers are called neurotransmitters, they are released and received by the brains nerve cells which are called neurons. Neurons are continuingly communicating with each other by exchanging neurotransmitters. This communication system is crucial so the brain can function correctly. There has been links from depression within the brain which creates problems with regard to the neurotransmitter’s serotonin, norepinephrine and dopamine. Antidepressant medications which are used to die down the symptoms of depression are also known to act upon these particular neurotransmitters and their receptors. A strength of the biological approach to depression is that it can be deterministic. The reason why is because it is more than possible to treat individuals with abnormal behaviour. This explanation can aid in individuals living a better life. A disadvantage would be that it doesn’t cover the experiences (tutor2u, n.d.) of distress, thoughts and feelings and does not take the environmental factors into consideration of the events, as it is a genetic approach to depression. A different strength biologically which can be the results are easily measured quantitatively and precisely so the treatments available are more than effective in the long run and are proven to work.