Why is vaporising used instead of smoking?

This is one of the few places in this field where the evidence points clearly in one direction. Burning anything and inhaling the smoke is harmful, the harm is avoidable, and avoiding it changes nothing about the therapeutic effect.

What actually differs

Burning plant material at high temperature breaks compounds down and creates new ones. Vaporising heats it enough to release the active compounds as a vapour without reaching combustion.

The products of combustion — tar, carbon monoxide, polycyclic aromatic hydrocarbons and other irritants — are the same class of substances that cause harm in tobacco smoking. They contribute nothing to the therapeutic effect. Avoiding them costs nothing clinically.

Vaporising also gives more consistent delivery, which matters when the aim is to find a reproducible dose rather than an effect.

What vaporising does not fix

It reduces one category of harm. It does not make inhalation harmless and it does not change anything about the cannabinoids themselves.

• Airway irritation, cough and throat discomfort are still common
• Long-term effects of habitual vapour inhalation are not fully characterised
• People with asthma or COPD may find any inhaled route unsuitable
• The cannabinoid risks are unchanged — impairment, anxiety, cardiovascular effects
• Device temperature and maintenance matter, and running too hot approaches combustion

Where an inhaled route does not suit, other routes are available and are covered in What forms do cannabis-based medicines come in?

The tobacco question

Mixing cannabis with tobacco remains common in the UK and is worth raising explicitly, because it changes the risk picture substantially.

It introduces nicotine dependence, which makes stopping harder, and adds the cardiovascular and cancer risks of tobacco smoking. Someone who has been using illicit cannabis this way and moves to a prescribed vaporised route is making a meaningful reduction in harm.

Prescribers ask about this. Answer honestly — the point is to get the treatment right, and a history of tobacco use changes the advice you should be given.

If you want to stop smoking, NHS stop smoking services are free and are more effective than going it alone.

Patient guide · Written by the Flora House editorial team · Last reviewed: 8 September 2026