The myths surrounding marijuana are apparently countless in number.
Marijuana: Burning Myths
One of the most well-known myths surrounding marijuana is that it damages human cell tissue and causes chromosomal breakage.  The National Academy of Sciences has rejected this myth and has indicated that cannabinoids are neither mutagenic nor carcinogenic. Another popular myth says that smoking pot causes reproductive system damage.  Smoking marijuana has been shown to lower sperm counts in humans temporarily, but the sperm levels return to normal once marijuana consumption ceases. 
Another claim states that marijuana reduces male testosterone levels: this theory has been challenged and refuted by several studies.
One of the most controversial myths is regarding cannabis use during pregnancy. There is little evidence implicating marijuana may harm a fetus. There are studies that support the claim that smoking marijuana may increase the risk of miscarriage, especially in early pregnancy.  However, it is recommended that an expecting mother should not use any drugs.
Medical Uses of Cannabis
Cannabidiol (CBD), one of the main active ingredients in cannabis is a very effective anti-inflammatory agent. Marijuana can be smoked or eaten to relieve the general pain, inflammation, and discomfort of arthritis.  It is an excellent stimulant of appetite and combats nausea and vomiting. 
Cannabis is also known to fight the symptoms of glaucoma by reducing the intra-ocular pressure. [7, 8] Multiple sclerosis patients who use cannabis report soothing of the painful muscle spasms and improved muscle coordination. 
Smoking cannabis may also relieve depression. However, some researchers claim that long-term marijuana smoking can have a depressant effect and reduce motivation, as well as that long-term smoking leads to irreversible, but minor cognitive deficits. 
A study connected marijuana with lower blood sugar in diabetics. 
Marijuana – Sex Stimulant or Depressant?
Presently, it is debatable whether marijuana acts as a sex drive stimulant (aphrodisiac) or suppressant. Marijuana affects different people in different ways. Some report an increased libido, while others report an inability to sustain an erection. Time and more reliable research might be able to help us sometime in future.
Three researchers from the University of Texas suggested that tetrahydrocannabinol, or THC, marijuana's active ingredient, may affect male sexual activity in two phases. In animal tests, they found that it first raises the level of testosterone and other sex hormones but later may lower hormone levels to below normal. 
The researchers measured levels of blood testosterone and luteinizing hormone, or LH, which stimulates testosterone production, within the first hour after feeding liquid THC to mice. They found that the testosterone level in all the mice jumped almost immediately to about six times its average amount. Moreover, mice receiving low doses of the drug maintained the high testosterone levels for the entire hour; those receiving much higher doses showed drastic drops in testosterone after 20 minutes to levels considerably below those of mice in the control group.
When a person smokes marijuana, the THC enters the bloodstream very rapidly. The almost instant effect of the drug on the testicles, as shown in this study, seemed to account for the dramatic reports of sexual arousal during and after smoking.
In normal sexual stimulation, it takes about 20 minutes for the production of luteinizing hormone, then travel from the pituitary to the testes, where it helps produce testosterone; in about the same amount of time the testosterone then enters the bloodstream and makes the trip back to the pituitary gland. This feedback system automatically shuts down when the brain senses an adequate level of sex hormone has been reached. Massive doses of THC disrupt the normal flow in this hormonal loop by triggering LH and testosterone production at the same time, which appears to cause a shutdown that sends hormonal levels falling 20 minutes after the drug is administered. No such testosterone drop was observed among mice that received low doses.
Low Dose Marijuana and Sexual Intercourse
Marijuana has been used as an aphrodisiac for thousands of years, yet ironically it has also been used to decrease sexual desire. At low to moderate levels of intoxication, users reported a heightened ability to communicate sexually with their partners and increased body awareness. 
When marijuana dosage was appropriate, it increased sexual stamina and skill, tactile sensation, length and power of orgasms, and emotional bonding between partners. People felt they became more loving, more willing to pay attention to the technical aspects of lovemaking and foreplay which women complain is often missing from the males sexual repertoire.
Modern users reported spiritual, emotional and psychological effects that mirrored ancient Tantric effects. They felt that intercourse was replenishing and balancing, and that orgasm was an energizing climax to sex, instead of a draining finale.
In regards to the claims that marijuana heightens sexual climax, there is scientific research that seems to discredit that. Chronic marijuana smokers do show signs of infertility — men may have lower sperm counts and women may have abnormal ovulation.
Read More: Therapeutic Uses Of Medical Marijuana
Erectile Dysfunction Drugs Combined with Marijuana Result in Risky Sex
Some young men experience erection problems and take erectile dysfunction drugs without a doctor's prescription. More than half of males who noted using erectile dysfunction (ED) drugs reported doing so to treat their erectile problems. Another 29% reported using the drugs to enhance sexual performance. 
Nearly two-thirds of those who used ED drugs reported mixing ED drugs with other drugs such as alcohol, marijuana, and cocaine. These boost sex drive and reduce inhibitions but diminish sexual performance. Combining ED drugs with alcohol or other drugs permits men in altered states to have risky sex, potentially contributing to unwanted pregnancies and the spread of sexually transmitted diseases.
To summarize, cannabis is said to increase libido and sexual desire. However, this drug is not aphrodisiac in the strict sense of the definition, as it does not consistently produce aphrodisiac effects as its main action. At low to moderate doses, cannabis is known to heighten sexual climax. Also, it has reported heightened ability to communicate sexually with their partners, and increased sensuality but may diminish sexual performance. But at high-doses, it results in decreased desire and chronic use results in dose-dependent increased/decreased desire and erection problems.