The demand for medical marijuana in Germany has skyrocketed since it was legalised in March last year.

The law allows patients to access cannabis on prescription and charge health insurance companies for it.

The law prompted a report by German health insurance company Techniker-Krankenkasse and the University of Bremen, which questions the effectiveness of cannabis for treating medical conditions.

The demand for medical marijuana in Germany has skyrocketed since it was legalised in March last year, placing a greater burden on the country's health insurance providers to cover the cost of prescriptions.

A new report published by German health insurance company Techniker-Krankenkasse, or TK, and the University of Bremen found that as of February nearly 16,000 patients nationwide had applied to be reimbursed for medical marijuana costs, compared to around 1,100 before the law came into effect.

The authors of the "Cannabis Report" also question the medical benefits of cannabis, often touted as an "herbal wonder drug."

"It is unclear which groups of patients cannabis helps in which dose — and in which form it should best be administered," University of Bremen professor and author of the study Gerd Glaseke said, according to Weser Kurier.

The review of studies showed the use of cannabis led to the possible improvement in cataracts and it has been found to stimulate appetite in AIDS patients.

However, Glaseke believes the side effects of cannabis still need to be investigated further.

TK manager Jens Baas said: "Before the health insurance company pays for it, any added benefit the drug may have must be justified."

Cannabis therapy is much more expensive than other drugs: treatments based on cannabis flowers cost between $350 and $2,600, more than four times as much as alternatives in the form of drops or tablets.

Even still, TK approved around two-thirds of the 2,900 applications it received last year, which worked out at a cost of about $2.7 million. The volume of applications across all statutory health insurance companies — around 16,000 — is a clear indication of the hype triggered by the drug.

In the meantime, however, doctors treating patients are obligated to provide clear proof and justification for the therapy.