What neurotransmitter is needed most in disease?

The neurotransmitter that is needed most in disease is dopamine. Dopamine is a neurotransmitter that is involved in a variety of brain functions, including movement, reward, and motivation. It is also involved in regulating attention, learning, and memory. Dopamine levels are decreased in a number of neurological diseases and disorders, including Parkinson's disease, schizophrenia, and attention deficit hyperactivity disorder (ADHD). As a result, dopamine replacement therapy is often used to treat these conditions.