Pain, anxiety and sleep disorders were the top three reasons for a prescription, University of Sydney's Lambert Initiative for Cannabinoid Therapeutics found.

Almost 250,000 scripts had been approved for Australians - including Hunter patients - since the national medicinal cannabis scheme began in 2016.

The researchers sourced their data from the Therapeutic Goods Administration's special access scheme.

"Unfortunately, we just don't know if these treatments were effective for these patients, but this data highlights where we can focus our attention next - to do focused studies and/or clinical trials," senior author Dr Elizabeth Cairns said.

"There is a clear, unmet need for effective drug treatments across a variety of conditions that may be being helped with medicinal cannabis. People are suffering and they are turning to this as an option. We need to study whether it is the best option."

She said it was better if academics could do the studies needed, rather than drug companies.

The study findings, published in Frontiers in Pharmacology, found "flower-based cannabis products containing THC" were being prescribed for anxiety, "particularly to males aged 31 or younger".

THC is a psychoactive part of the cannabis plant that can produce feelings of relaxation. CBD is also a relaxant, but does not produce the same effects as THC.

Research shows too much cannabis can cause anxiety, but the strain of cannabis being used and the method of ingestion are factors in this.

Dr Cairns said the evidence for medicinal cannabis for anxiety was limited to only a few studies investigating CBD-dominant products.

She said it would be worth doing clinical trials into the use of cannabis flower products [buds] for anxiety.

People with anxiety and pain, she said, might be using cannabis to give them a quick dose that does enough to alleviate their suffering. Along with buds, oil, capsules, lozenges and spray products were among the prescribed products.

Dr Cairns said the Lambert initiative was interested in developing cannabinoids into therapeutics and improving access to safe and effective medicinal cannabis in Australia.

She cited a study that said researchers were seeking to develop "the holy grail in cannabis research", a medicinally-active formulation that helps treat anxiety or mood disorders without causing anxiety.

Stigma and the legal and political status of cannabis across the world has hampered clinical research into use of the plant for medicinal purposes.

Nonetheless, human civilisations have used cannabis as plant medicine for thousands of years.

University of Newcastle Professor of Clinical Pharmacology Jennifer Martin has previously told the Herald that determining suitable doses of medicinal cannabis will be crucial for the plant to advance as a treatment for health conditions.

The University of Sydney study, whose lead author was Sara MacPhail, said the "recent worldwide renaissance in the use of cannabis for medical purposes is supported by evidence of efficacy, albeit somewhat variable".

This use was across a range of conditions, including chronic pain, muscle spasticity in multiple sclerosis, chemotherapy-induced nausea and vomiting, palliative care and severe forms of childhood epilepsy.

"Evidence around the efficacy of cannabis in certain health conditions continues to evolve, with rapidly increasing global numbers of randomised controlled trials and preclinical research.

"However, there remain many conditions for which clinical evidence is minimal or ambiguous, with systematic reviews often highlighting a paucity of high quality randomised control trials to support current prescribing."

The study said any practitioner can apply to the TGA "to prescribe a medicinal cannabis product to a patient for any condition, provided they can justify prescribing based on the available evidence".

Cannabis was being used through the special access scheme for conditions in categories such as as mental and behavioral disorders, diseases of the nervous system, neoplasms and diseases of the musculoskeletal system and connective tissue.

"There are currently at least 375 different unregistered MC [medicinal cannabis] products in Australia that can be supplied via the SAS-B [Special Access Scheme-B] and AP [Authorised Prescriber] schemes."

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