It has also been recorded by Cobb (1979) “that morbid jealousy may be present with all types of cerebral insult or injury.” "It has been suggested that morbid jealousy may potentially arise in response to reduced sexual function”. Cobb (1979) drew attention to the elderly man whose waning sexual powers were insufficient to satisfy a younger wife. Mullen (1990) considered morbid jealousy to be associated with four features:
An underlying mental disorder emerges before or with the jealousy
The features of the underlying disorder coexist with the jealousy
The course of morbid jealousy closely relates to that of the underlying disorder
The jealousy has no basis in reality

Personality
People who are very insecure, or even fearful, are more likely to become anxious, or question their partners commitment to them. “Insecure attachment style correlates strongly with borderline personality disorder” (Kingham and Gordon). Environmental
Some people even believe that someone who is morbidly jealous might suspect that he or she is being drugged or given some kind of substance that might decrease their sexual potency, or they might even be under the impression that their significant other has somehow received a sexually transmitted disease from another person while the subject is unaware. Epidemiology
There is no known prevalence of morbid jealousy; currently there is no community survey tracking its existence in individuals. As of late, it is considered to be a rare occurrence. Still, many counselors encounter cases of morbid jealousy.
“In two studies, morbid jealousy was present in 27% and 34% respectively of men recruited from alcohol treatment services” (Shrestha et al., 1985; Michael et al., 1995). Amphetamine and cocaine increase the possibility of a delusion of infidelity that can continue after intoxication stops. (Shepherd, 1961). Assessment
In an attempt to counsel or treat the morbid jealousy of an individual, proper and thorough assessment must be employed. This approach is broad in nature, but necessary so as to provide adequate information that will aid in the possible reparation of a dynamic containing a morbidly jealous person. To begin, a careful history should be taken of both partners if possible; separate and together. It is imperative that a full and detailed psychiatric history and mental state examination be recorded for the jealous partner; doing so may enable one to distinguish whether the jealousy is obsessional or delusional in nature. It is also possible that the jealousy may be the result of a thought that has been given too much importance. Considering that jealousy is a very delicate issue, any reference made to it should be approached carefully and with tact. It must be kept in mind that the jealous individual may be displacing blame for their issues onto their partner and their alleged infidelity as opposed to their own behavior. If there is any history of relevant or related mental illness and substance misuse it should be noted as it may possibly be a contributing or aiding factor.