Note: This advice is given by the CAP Executive about non-broadcast advertising. It does not constitute legal advice. It does not bind CAP, CAP advisory panels or the Advertising Standards Authority.


What is Phototherapy?
What is SAD?
What types of claim are likely to be a problem?
Is the phototherapy product a medical device?

What is Phototherapy?

Phototherapy, also sometimes known as Light Therapy, involves the shining of light onto the body or face.  It works on the principle that natural daylight which is lacking at certain times of year (particularly in winter months) can be replenished using artificial light.  

What is SAD?

CAP understands that Seasonal Affective Disorder (SAD), also known as ‘winter depression’, is a mood disorder whose sufferers experience depressive symptoms in the winter or, less frequently, in the summer. It reoccurs year after year with normal mental health throughout most of the year. The most difficult months for SAD sufferers tends to be January and February, with symptoms often subsiding during the spring.

What types of claim are likely to be a problem?

Because SAD is often associated with depression, the condition is considered by the ASA to be one for which medical supervision should be sought. As such, there is a risk that presenting a device or a therapy as a treatment for SAD could be seen to discourage essential treatment, unless that treatment is carried out under the supervision of a suitability qualified health professional (Rule 12.2). 

In 2019, the ASA considered advertising claims to treat SAD using vitamin D and UV exposure (through sunbeds).  In that case the ASA ruled that because it had not seen evidence that the sunbed treatment was carried out under the supervision of a suitably qualified health professional, claims to treat that condition discouraged essential treatment for SAD (Unvilla Ltd, 6 November 2019).

Marketers are reminded that even if are able to demonstrate that the phototherapy treatment of SAD is being carried out under the supervision of a suitably qualified health professional, they would still need to hold clinical evidence to support claims of efficacy (Rule 12.1).

Many years ago CAP had understood that there was evidence of efficacy for the treatment of the symptoms of SAD using phototherapy and that such claims were considered to be generally acceptable provided the marketer could demonstrate that the device or therapy being marketed emitted light between 3,000 and 10,000 lux.  However, since that time the NHS has published its own advice on treatments for SAD, suggesting there was mixed evidence with regard the efficacy of light therapy.  That does not mean that efficacy claims are no longer acceptable, but it does indicate that the ASA is likely to expect marketers to hold robust clinical evidence to support claims that their phototherapy treatment or device can be used to treat SAD, or the symptoms associated with SAD.

Marketers are reminded that they would also need to hold clinical evidence for any other advertising claims about the benefits of Phototherapy. 

See CAP Guidance on Substantiation.

Is the phototherapy product a medical device?

If the phototherapy product in question is a device (such as SAD lamp) and the intended purpose is for treating a medical condition, it may fall under the definition of a medical device.  Medical devices need to be appropriately certified (CE-Marked) before making marketing claims of a medical purpose (rule 12.1)

CAP recommends that marketers seek advice from the Medicines and Healthcare products Regulatory Agency (MHRA) to establish if the product needs to be Certified (CE marked) as a medical device before it is marketed in the UK for that purpose. This MHRA guidance on medical devices explains the position further. 


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