His research indicates that "[a] prominent and sharply raised lip tubercle has been associated with greater odds (odds ratio = 12.3) of ever having a vaginal orgasm, and also with greater past month vaginal orgasm consistency (an effect driven by the women who never had a vaginal orgasm), than less prominent lip tubercle categories." However, lip tubercle was not associated with social desirability responding, or with orgasm triggered by masturbation during penile-vaginal sex, solitary or partner clitoral or vaginal masturbation, vibrator, or cunnilingus.An empirical study carried out in 2008 provides evidence for Freuds implied link between inability to have a vaginal orgasm and psychosexual immaturity. In the study, women reported their past month frequency of different sexual behaviors and corresponding orgasm rates and completed the Defense Style Questionnaire (DSQ-40), which is associated with various psychopathologies. The study concluded that a "vaginal orgasm was associated with less somatization, dissociation, displacement, autistic fantasy, devaluation, and isolation of affect." Moreover, "vaginally anorgasmic women had immature defenses scores comparable to those of established (depression, social anxiety disorder, panic disorder, and obsessive–compulsive disorder) outpatient psychiatric groups." In the study, a vaginal orgasm (as opposed to a clitoral orgasm) was defined as being triggered solely by penile–vaginal intercourse. According to Wilhelm Reich, the lack of womens capacity to have a vaginal orgasm is due to a lack of orgastic potency, which he believed to be the result of cultures suppression of genital sexuality.
Multiple orgasms are more commonly reported in very young men than in older men. In younger men, the refractory period may only last a few minutes, but last more than an hour in older men.An increased infusion of the hormone oxytocin during ejaculation is believed to be chiefly responsible for the refractory period, and the amount by which oxytocin is increased may affect the length of each refractory period. A scientific study to successfully document natural, fully ejaculatory, multiple orgasms in an adult man was conducted at Rutgers University in 1995. During the study, six fully ejaculatory orgasms were experienced in 36 minutes, with no apparent refractory period. Females
Orgasmic factors and variabilities
In women, the most common way to achieve orgasm is by direct sexual stimulation of the clitoris (meaning consistent manual, oral, or other concentrated friction against the external parts of the clitoris). General statistics indicate that 70–80% of women require direct clitoral stimulation to achieve orgasm, although indirect clitoral stimulation (for example, via vaginal penetration) may also be sufficient. The Mayo Clinic stated, "Orgasms vary in intensity, and women vary in the frequency of their orgasms and the amount of stimulation necessary to trigger an orgasm." Clitoral orgasms are easier to achieve because the glans of the clitoris, or clitoris as a whole, has more than 8,000 sensory nerve endings, which is as many (or more in some cases) nerve endings as are present in the human penis or glans penis.