Diseases of the central nervous system (CNS) can be categorized either as psychiatric or neurological. Psychiatric diseases are characterised by impairment of an individual's normal cognitive, emotional, or behavioural functioning, and are caused by social, psychological, biochemical, genetic, or other factors, such as infection or head trauma. They are also often referred to as mental illnesses. The most common psychiatric diseases include, for example, depression, schizophrenia (psychosis), anxiety disorders as well as abnormal behaviour (e. g. eating disorders) and addiction. In the classic neurological diseases on the other hand, psychological disturbances occur often only as ancillary symptoms. Neurological diseases encompass a wide variety of indications ranging from seizures such as epilepsy and migraine, to genetic (dystrophies), immunological (multiple sclerosis), infectious (meningitis), vascular (stroke), neurodegenerative (Alzheimer's disease), and traumatic (spinal cord) lesions of the central nervous system.
Neurodegenerative diseases include Alzheimer's disease, Parkinson's disease, Huntington's disease, Creutzfeldt Jakob disease, Spinal Muscle Atrophy (SMA), and Amyotrophic Lateral Sclerosis (ALS, or Lou Gehrig's disease). A common element of neurodegenerative, vascular, and traumatic neurological diseases is the loss of neurons, and the functional deficit resulting from it. Since there are no or only insufficient therapies for neurodegenerative diseases, the demand for novel therapeutic approaches is immense.