It is rare to find morbid jealousy in its pure form. It is usually found in combination with an underlying mental disorder. People with paranoid personality or borderline disorder are more susceptible to morbid jealousy. Also people with an insecure attachment style are more prone to this syndrome. They are more likely to feel inadequate, insecure and inferior which may prompt morbid jealousy. Drug and alcohol abuse are common among people with morbid jealousy. Although these are not the causes of the jealousy, substance abuse would exacerbate the syndrome.
Many suffering from this syndrome realize that their feelings of betrayal are unfounded and yet cannot free themselves from the intrusive barrage of thoughts relating to their partners infidelity. Their behaviours, such as checking pockets, emails, drawers, bed linen, medicines etc. of their partner become compulsive. Stalking or hiring a private detective are also common things people with morbid jealousy do.