Calvin works at a paper manufacturing company. The bleaching agents used by the company are toxic in nature and as a result of being exposed to these substances, Calvin has been experiencing intense depressive episodes due to changes in his brain functioning. From the available information, it would be most accurate to conclude that ________ causes are responsible for Calvin's depression.

Biological causes of depression could be described as biological or chemical substances that could affect the hormones or brain of individuals which could lead to depression. This could be accessible through inhaling of chemicals in toxic manufacturing environment. Many people who works in some of this environment are affected psychologically which now reflects on their behaviour, some are usually aware of this and some aren't, some who are aware change jobs with time. It could be described that this is what Calvin is going through.