Yes, the study of neurotransmitters is part of the study of biological psychology. This is because neurotransmitters have a profound effect on the human mind. For instance, low levels of serotonin are linked to conditions such as depression and OCD. Drugs such as SSRIs increase the levels of serotonin, and are often helpful to people with these conditions.
Another important neurotransmitter is dopamine. Low levels of dopamine are associated with schizophrenia.   _{Your Comment}