Obsessive compulsive disorder. Computer artwork of a DNA (deoxyribonucleic acid) autoradiogram spelling out OCD (obsessive compulsive disorder). OCD is an anxiety disorder characterised by incontrollable anxious thoughts and or rituals. Its cause is not known although it is thought that some people may be genetically predisposed to the condition as it is more common in the relatives of people with OCD or Tourette's syndrome. Treatment is with antidepressant drugs and cognitive behavioural therapy. The bands of an autoradiogram show the sequence of nucleotide bases in a sample of DNA.