For many people, the sun's return is the perfect antidote to perk up their mood and give them new vim and vigour.

However, this pick-me-up is not felt by everyone during spells of good weather.

In fact, there are some people who struggle with a condition known as 'reverse SAD' or 'summer SAD' (seasonal affective disorder).

Reverse SAD is quite similar to seasonal affective disorder that occurs during the winter. According to mental health charity Mind's website, with reverse SAD people experience 'depressive symptoms occurring in summer'.

The condition's symptoms include anxiety, issues sleeping, agitation, loss of appetite, and weight loss. 

Summer SAD is quite rare, with less than one tenth of SAD cases being reverse SAD, according to Psychology Today.

It is thought that the presence of too much sunlight causes the onset of summer SAD, as increased daylight can lead to modulations in melatonin production.

An alternative theory is that those longer daylight hours cause people to stay up later than usual, throwing off their circadian rhythms.

As well, temperature may have a part to play in the condition, which comes as no surprise when you think about how agitated people can become in the heat.

Summer SAD tends to be more prevalent in places with warmer summers, so, for example, those in the southern United States would experience it more than those in the north.

Those with the condition may start to experience symptoms around March that last until autumn.

Those that suffer from reverse SAD can check out Mind's guide to treating this complex condition or consult their doctor.