For the first time since its inception back in 1987, the High Times' "Cannabis Cup" will be held on American soil on April 20, 2013 in Denver, Colorado. The two-day expo will allow judges and marijuana supporters to come out and compare different types of cannabis and discuss different cultivation methods.

Although the sale and use of marijuana is still illegal under federal restrictions, 18 US states (and D.C.), including Colorado, have currently enacted laws to prohibit medical marijuana use so long as it's recommended by a physician.

This celebration of weed and all things weed related is expected to draw in tens of thousands of red eyed pot advocates, most of which will have only one question on their smoke riddled minds: How do I get my hands on a medical marijuana identification card?

Here are the seven most common reasons medical marijuana is prescribed:

1. Chronic Neck/Back/Spine Pain

In July 2011 the article Who Are Medical Marijuana Patients? was published in the Journal of Psychoactive Drugs. Among the reasons for prescribing medicinal marijuana, pain or spasms in relation to the human spinal cord ranked in at number one.

2. Migraine/Headaches

Aside from physical pain relief, the active ingredient in marijuana, THC, can also act as an anti-inflammatory agent. Marijuana introduced to the brain has been known to stimulate nerve cell endings, alleviating both mild and intense headaches.

3. Sleeping Disorders/Anxiety/Depression

Difficulty falling or staying asleep has been linked to increased anxiety which in turn can lead to psychological disorders like depression. Past studies mark a release of melatonin when THC is introduced to the system that can help someone relax and fall asleep quicker.

4. Gastrointestinal Disorders

Stomach illnesses such as irritable bowel syndrome, Crohn's disease and ulcerative colitis are known to cause nausea, constipation, diarrhea, and uncomfortable cramping. All these symptoms can be traced back to intestinal inflammation which can be eased by the anti-inflammatory properties of THC.

5. Glaucoma

Medical conditions that affect the eye such as glaucoma are primarily caused by a significant amount of pressure on the wall of the eye. Marijuana does the job of relieving this added pressure on the eye which can ultimately lead to obstructed vision.

6. AIDS/HIV

HIV and AIDS patients are regularly prescribed medical marijuana in states where it's legal. Not only can THC improve neurological receptiveness with HIV and AIDS patients, it is also praised as a possible remedy for symptoms that include nausea and mood changes.

7. Cancer

Other than alleviating cancerous symptoms such as loss of appetite and nausea, recent studies have shown that THC properties can block cancerous cells from the immune system and inhibit the growth of tumor producing blood vessels.

In 1996 the state of California passed Proposition 215 making it legal within the state for doctors to prescribe patients medical marijuana for necessary purposes. Then in 2003 the state senate introduced the Medical Marijuana Program Act, or Bill 420, to clarify the application of Prop 215. California became the first municipality in the US to do so.

The California Department of Public Health lays out the requirements for a US citizen to receive a medical marijuana identification card which include a doctor's recommendation, proof of identification (i.e. state driver's license or passport) and proof of county and state residence (i.e. utility bill or rent receipt).

Patients are required to register their application in the county they currently reside in and must appear in person so that the fee requirements can be paid and their picture, which will appear on their ID, can be taken.

The CSPH also offers a directory comprising all of the countywide health agencies where one can be tested for medical marijuana use.