Litepod SAD lamp with mains charger, made by S.A.D. Lightbox Company, Lewknor, Oxfordshire, in 2013. Used for the treatment of seasonal affective disorder. Unidentified plastic and metal

First described in 1984, seasonal affective disorder (SAD) is a form of depression felt more in autumn and winter. It is thought it might be triggered by reduced exposure to ultraviolet (UV) light from the sun. Lightboxes like this are one treatment option, although they are not available on the NHS. Many people buy their own as well as using other treatments like medication and talking therapy.