What Is Seasonal Affective Disorder (SAD)?

Seasonal Affective Disorder (SAD) is a recognised form of depression that typically occurs during the autumn and winter months when daylight hours are reduced.

Common symptoms include:

● Persistent low mood

● Fatigue and low energy

● Difficulty concentrating

● Changes in sleep and appetite

● Loss of motivation

● Increased anxiety

For many people, SAD has a direct and significant impact on work performance.

Is SAD a Valid Reason for Sick Leave in the UK?

Yes. SAD is a legitimate medical condition and can justify sick leave if it affects your ability to work safely or effectively.

UK employment law does not distinguish between:

● Physical illness

● Mental illness

● Seasonal mental health conditions 

If SAD symptoms impair your functioning, sick leave is appropriate.

Do You Need a Sick Note for SAD?

The standard sickness rules apply:

● You can self-certify for the first 7 calendar days

● A sick note is required only if symptoms last longer than 7 days 

This applies even if symptoms fluctuate rather than remaining constant.

What Will a SAD Sick Note Usually Say?

Most sick notes for SAD will:

● Avoid naming the condition explicitly

● Focus on functional impact

● Recommend time off or temporary adjustments

A note may state:

● “Not fit for work”, or

● “May be fit for work” with adjustments such as reduced hours or remote work

Can Employers Challenge SAD-Related Sick Leave?

Employers:

● Cannot dismiss SAD as “just winter blues”

● Cannot demand diagnosis details

● Must treat mental health fairly

If SAD meets the legal definition of a disability (long-term, substantial impact), additional protections may apply.

Can You Get a SAD Sick Note Online?

Yes. SAD is well suited to remote assessment, as diagnosis is based on symptom history and impact rather than physical examination.

A responsible service will assess:

● Duration of symptoms

● Functional impairment

● Risk factors

Services like Dr Sicks can issue sick notes when clinically appropriate, or recommend further support if needed.

Key Takeaways

● SAD is a recognised medical condition

● Sick leave rules are the same as other illnesses

● Employers must act reasonably

● Online assessment is often appropriate