Around 7 of this group are women.) Symptoms include depression, withdrawal, lack of energy and concentration, desire to sleep longer and increased appetite - and even if you're not prone to these, colds and coughs can be difficult to avoid.
Why? Ultimate Wellbeing Specialist Akcelina Cvijetic explains.
"According to traditional Chinese Medicine and the Law of Five Elements, autumn is the season associated with our immune system and especially lungs," Cvijetic says.
"Typically, it is the time of year when the temperatures suddenly plummet and our body is trying to adjust to these seasonal changes.This is why we tend to be more prone to illness during this time of year."
And if you struggle to shift the sniffles when they do arrive, you can blame it on a change in melatonin synthesis.
"More melatonin, the 'sleep hormone and neurotransmitter', is produced during the longer nights," Cvijetic adds. "This has a knock on effect with serotonin, the 'feel good hormone and neurotransmitter.'"
Increasing serotonin levels is the key to boosting mood and immunity. The easiest way to do this? Through your diet.
"The best food choices include foods rich in tryptophan – a pre-cursor of serotonin," says Cvijetic.
Tryptophan can be found turkey, beans, whey protein, cottage cheese, avocado and bananas - and as the brain needs fatty acids to run efficiently, it's also important to incorporate omega-3 rich foods like oily fish, chia and flax seeds.
Cvijetic also recommends including warming spices (turmeric, chili and cayenne pepper) in soups and stews as well as stocking up on other immune-boosting fruit and vegetables.
Now's the time to add garlic, onions, goji berries, kiwis, pomegranates and ginger to your shopping list.