Causes of Sexual Dysfunctions
Causes of Sexual Dysfunctions
"Sexual dysfunctions are an important public health concern, to which general health and emotional problems contribute" (10). What is a sexual dysfunction? A sexual dysfunction is any condition that inhibits someone's ability to enjoy sex. Some common sexual dysfunctions are: hypoactive desire disorder (low sex drive), hyperactive sexual disorder (high sex drive), sexual aversion disorder, lack of lubrication (females), impotence (male erectile disorder), premature ejaculation, vaginismus (prolonged contractions of the vaginal wall that cause painful intercourse), or failure to orgasm during sex (8). In a study of happily married couples, 14% of men and 15% of women reported that they were either not very satisfied or not at all satisfied with their sex lives. In another study by Laumann in 1992, it was found that the prevalence of sexual dysfunction is 43% in women and 31% in men (10). Are these numbers surprising? What is causing this lack of sexual fulfillment?
Did you ever wonder why sexual desire varies from person to person? Or why and how your sexual drive can change over time? Did you ever wonder what causes things to go wrong sexually - sexual dysfunctions? What is controlling YOUR sexual desire?
Innervations of the organs of sexuality are mediated primarily through the autonomic nervous system (12). The autonomic nervous system is the part of the vertebrate nervous system that regulates involuntary action, as of the intestines, heart, and glands, and that is divided into the sympathetic nervous system and the parasympathetic nervous system (1). It is generally assumed that the parasympathetic system activates the process of erection via impulses that pass through the pelvic splanchnic nerves (S2, S3, S4), which cause the smooth muscles of the penile arteries to dilate. The sympathetic (adrenergic/adrenalin) system is responsible for ejaculation. Similarly for women, the sympathic system facilitates smooth muscle contraction of the vagina, urethra, and uterus that occurs during orgasm.
"The autonomic nervous system functions outside of voluntary control and is influenced by external events (for example, stress, drugs) and internal events (hypothalamic, limbic, and cortical stimuli)" (12). So, it is not surprising, therefore, that erection and orgasm are so vulnerable to dysfunction.
There are many possible psychological disorders that could cause a person to be sexually unsatisfied. If a person has a psychological disorder such as bi-polar disorder, schizophrenia, epilepsy, or depression - they tend to enter states of extreme fear, paranoia, or anxiety more often than a person without their disorder. These states are not normal states of consciousness for a healthy person, and many of these abnormal states of consciousness inhibit sexual interest (9). For example, a bi-polar person experiences non-normal states of extreme bliss or extreme depression. During each non-normal state of consciousness, the bi-polar person will be too consumed by either their elation or their depression to feel any sexual desire. Therefore, a person's sexual desire is related to the amount of time spent in non-normal states of consciousness.
Not only the psychological disorder itself can cause abnormalities in sexual desire, but so can the treatment of the disease. Drugs used to treat some psychological disorders - such as depression - can alter sexual desires by disturbing the normal processes in the brain that deal with desire and sexual arousal. Certain chemical agents such as antihypertensive, anticonvulsant, serotoninergic antidepressant and neuroleptic drugs may cause a loss of libido - sex drive (12). These drugs alter the production and uptake of certain chemicals called neurotransmitters in the brain that have been found to alter sexual desire/performance. Some of these neurotransmitters are: dopamine, epinephrine, norepinephrine, and serotonin. All have effects on sexual function. For example, an increase in dopamine is presumed to increase libido. Serotonin produced in the upper pons and mid-brain is presumed to have an inhibitory effect on sexual function (12).
There are other medical conditions in addition to psychological disorders that can be the cause sexual problems. In the U.S. there are two million men who are "impotent because they suffer from diabetes mellitus; an additional 300,000 are impotent because of other endocrine diseases; 1.5 million are impotent as a result of vascular disease; 180,000 because of multiple sclerosis; 400,000 because of traumas and fractures leading to pelvic fractures or spinal cord injuries; and another 650,000 as a result of radical surgery, including prostatectomies, colostomies, and cystectomies" (12). Some of the injuries are of the abdomen, lower spinal cord, or pelvic vascular areas, which can compromise circulation to the genitalia or sensory nerves to/from the genitalia - producing impotence or other changes in normal sexual responses.
In addition to psychological disorders, drugs, and varying medical conditions being the cause of sexual dysfunction, injury and/or brain surgery can also cause a range of affects on a person's libido (4). Examining the outcome of damage to certain, specific areas of the brain can help us understand the roles that those parts of the brain play in sexual drive/performance.
There are 4000 serious head injuries that occur each year in the U.S., of which about 100 are survivors. The disturbance of sexual functioning in these head injury survivors is the rule rather than the exception (4). Sexual drive, having to do with structures deep in the brain, are rarely disturbed by non-penetrating head injury. It is sexual motivation and initiation that are damaged by blunt frontal lobe trauma.
Experimentation with animals has demonstrated that the limbic system is directly involved with elements of sexual functioning. In all mammals the limbic system is involved in behavior required for self-preservation and the preservation of the species (12). The limbic system is the "link between higher cortical activity and the lower systems that control behavior" (3). It controls the neuroendocrine system, autonomic system, olfactory sensory processing, emotions and motivation, and memory. The limbic system is interconnected nuclei of the olfactory bulb and orbitofrontal cortex, amygdala, hippocampal formation, hypothalamus, anterior and mediodorsal nuclei of thalamus, septal nuclei, and the Limbic ring of neocortex (7).
Kluver and Bucy proved that the limbic system is involved with sexual functioning in their experiment with monkeys. The monkeys in their experiment were aggressive and raging prior to the operation. The operation consisted of the removal of the monkey's temporal lobe. After the operation the monkeys were docile, orally fixated, and had increased compulsive and sexual behaviors (2). Their findings led to the so-called Kluver-Bucy Syndrome. Humans can get Kuver-Bucy Syndrome when their temporal lobes get damaged from such things as tumors or surgery. Humans with this disorder also experience a disturbance in sexual function just as the monkeys did (3).
Temporal lobe epilepsy is another way in which the temporal lobe might function inadequately and cause sexual dysfunction. There is a high frequency of sexual disturbance in patients with temporal lobe epilepsy. Gastaut and Collomb (1954) were the first to draw attention to hyposexuality after specific inquiry in 36 patients with temporal lobe epilepsy. More than two-thirds showed marked diminution or absence of interest, appetite or sexual activity. Other forms of focal and generalized epilepsy appeared to be unassociated with such problems. Frequently, there was "a remarkable lack of sexual curiosity, fantasies or erotic dreams, yet little to suggest inhibition since the patients talked easily and without reserve about such matters" (12).
The amygdala has a large number of sexual phenomena associated with it. One of the more interesting is the observation that gay men have more connections between the amygdala on each side of the brain than straight men (9). The amygdala manages our emotions and helps to manage our states of consciousness (9). These normal and non-normal states of consciousness have a lot to do with sexual dysfunction (e.g. hyposexuality) as was discussed previously with psychological disorders.
Physiological disorders, medications, certain medical conditions, injury and/or brain surgery are only some of the causes of sexual dysfunction. Examining the neurological causes of sexual dysfunction will allow us to better understand the workings in our brain that have to do with sexual desire - and with this knowledge and better understanding we can hopefully help the many people in our society that suffer from sexual dysfunctions.
09/22/2005, from a Reader on the Web
I read your atricles on line about neuroscience and sexuality and also about the anygdala and sexuality. I am 24 male and I have suffered with a complete lack of desire for the last 3 years after having taken a drug called Propecia (for 5 months) for male pattern baldness. The drug inhibits the production of DHT in the body which can help to stop balding, but is known to also affect libido & impotency in some men. I was late going through puberty when I was younger so even though I took Propecia when I was 21, I think I had the pubertal stage of a 17 yr old. I have been to just about every hormonal expert in America and I do not seem to have a problem nor do I respond at all to Testosterone injections. I had a very normal libido before I took the drug and now I have next to nothing, a sexual thought has not crossed my mind in years without me forcing it. I also have next to no visual stimulation at all and I fell very numbed emotionally (especially romantically obviously) as well a I have also seen a number of sexual psychologists ( Dr Perelman, if you have heard of him) who seem to think that I may have caused some neurological damage and there does not seem to be any significant emotional problem which could have caused this. I believe after speaking with a number of doctors (yet no neurologists) that the lack of DHT at stage when my brain was still developing sexually may have caused some neurological deformation or damage, potentially to the amygdala. I was wondering if you could refer me to or tell me of a neurologist (preferrably in NYC) who may be at least willing to check if I have experienced any neurological damage or anything like that. I am not concerned about the potential costs involved, this has been incredibly devastating to my life and I am willing to do just about anything to get to the bottom of it. I might also add that I know of hundreds of other men who have experienced the side effects of this drug permanently after stopping up to 7 years ago. We are trying to get attention for the issue, but it is a difficult problem to trace. Thank you for your time.