For some, frosty mornings and dark nights are a welcome change after long hot summer days. For others, the winter months are synonymous with low mood, lethargy and reduced energy levels.

The term “winter blues” isn’t an official medical term. It generally refers to a mild and temporary drop in wellbeing and is fairly common. This is triggered by reduced levels of sunlight, which impact the production of serotonin and melatonin, the neurotransmitters that regulate mood, sleep and mental outlook.

Although some symptoms overlap, winter blues differ from seasonal affective disorder (SAD). A subtype of depression, SAD affects an individual’s ability to lead a normal life during the winter months.

SAD symptoms can include oversleeping, overeating, feelings of worthlessness and even thoughts of death, although not everyone will experience these. The cause of SAD isn’t fully understood. One hypothesis is that most patients become depressed in winter because of a delay in circadian rhythms with respect to the sleep/wake cycle. Some people have symptoms in summer and feel better in winter. Genetics may play a role as cases can run in families.

Feeling less active or wanting to hunker down is a normal response to reduced light levels. 

Whereas SAD symptoms can last up to five months, the winter blues are short-lived. The winter blues can become an issue if they last for more than a few weeks or become more intense, so it’s important for optometrists to take proactive steps to identify the early-warning signs so that they can protect their wellbeing and seek professional help if necessary.