Do you have ‘flu fatigue’?

This is the time of year when many of us feel depleted, pushing on doggedly despite suffering repeated bouts of colds and possibly even flu. We dismiss our low mood and cognitive impairments simply as signs of weakness, of our inability to cope.

But could these symptoms – or some of them, at least – be manifestations of the illnesses themselves? And even if they’re not, wouldn’t it be better to look for ways to feel better, instead of blaming ourselves and lowering self-esteem still further?

Infectious diseases such as colds and flu have a real effect on cognitive functioning. Lucile Capuron and colleagues at the Neurobiological Laboratory in Bordeaux tested memory and attentional processes of 91 adults.

Thirty of them were healthy at the time of testing, 29 were suffering from flu-like symptoms including fever, and 32 had flu-like symptoms but no fever.

Compared to healthy participants, those with flu – whether they had a fever or not – performed less well on all the tests, particularly those that required them to manage larger amounts of information.

Andrew Smith and colleagues at the University of Bristol has studied the effects of having a cold on both mood and cognitive processes. Compared to healthy controls, participants with colds showed impaired tracking abilities and reaction times, and scored less well on attention tasks – although their memory was not affected. Those with colds also had lower mood.

When you’re exposed to infection, your body’s reaction is to activate your immune system. This activation, necessary to fight the invading bacteria or virus, causes cellular inflammation.

Some researchers think there may be an association between such inflammation and depressive symptoms such as low mood, fatigue and lack of motivation and interest.

Elaine Setiawan at the Centre for Addiction and Mental Health in Toronto observed the brains of individuals suffering from major depression, and noted the same sort of cellular inflammation seen in individuals fighting acute infection.

It’s understandable to feel depressed when you’re ill, even if there is no physical basis. But whatever the cause, it’s a good idea to heed your body’s warning to slow down so your immune system can fight the infection effectively.

The more you ignore your symptoms and push on instead, the more stressed you’ll become – and therefore the more inflammation you’ll trigger. This can lead to a cycle of repeated illness.

A much better approach is to stop trying to do and remember everything, and take some time off to rest. Not only will your self-esteem rise when you demonstrate to yourself that you deserve a chance to recover, you may also lessen the impact of future bouts of illness.

Barbara Hewson-Bower and Peter Drummond at Murdoch University in Australia recruited 45 children who were suffering from recurrent bouts of upper respiratory tract infections.

After teaching them to relax and make use of positive imagery, the children experienced shorter bouts of illness, reported milder symptoms and had higher mood scores – both after 13 weeks, and one year later.

• Linda Blair is a clinical psychologist and author of Siblings: How to Handle Rivalry and Create Lifelong Loving Bonds. To order for £10.99, call 0844 871 1514, or visit books.telegraph.co.uk.

• Watch her give advice at telegraph.co.uk/wellbeing/vide o/mind-healing