Christmas is over. Term is starting, the rain is falling… and any New Year’s resolution to eat more healthily is easily threatened by all the leftover Christmas cookies. We should not be too quick to condemn holiday indulgence, though; a growing body of research shows that holiday treats might be good for our brains – or, at least, might make our brains work in very interesting ways.

The idea that food and drink can alter our mental state is not new. For millennia, humans have taken herbal medicine, drunk wine, and even ingested fungi to provoke visions. Magic mushrooms might not appear at Christmas lunch, but holiday menus still contain several supposedly psychoactive ingredients: spices, wine, and fungi, often in the form of Stilton cheese.

The cheese board is not an obvious choice for sharpening your wits – or ‘tripping’ – but what about the urban myth that cheese causes bad dreams? ‘Myth’, because there is only one academic paper that mentions cheese dreams. This was a 1964 letter to the British Medical Journal, wherein a patient developed terrifying nightmares after combining his blood pressure medication with a dose of aged Cheddar. Even so, theories about the link between bedtime cheese and nightmares still abound; it’s thought that the bacteria and fungi in cheese produce psychoactive compounds similar to the ones in magic mushrooms.

The cheese myth is so well-known that the British Cheese Board went as far as commissioning two studies to investigate the effect of eating cheese before bed on dream quality. The first study was less reliable – it lacked a control group! – but volunteers for the second study in 2014 reported that eating cheese not only failed to trigger nightmares but also helped them sleep better. This seems logical because cheese does contain the amino acid tryptophan, which the brain needs to produce melatonin, a signalling molecule that regulates sleep. Unfortunately, you would need to eat Stilton by the pound to affect melatonin synthesis, so why cheese might be a recipe for sweet dreams is still unknown.

So much for savoury foods; what about Christmas sweets? Those innocent-looking gingerbread men conceal a host of psychoactive compounds, some of them so powerful that ‘spice abuse’ is a real clinical problem. So much so, in fact, that the journal Current Psychiatry published a 2014 review showing clinicians how to spot possible cases. Nutmeg is the major culprit, having been implicated in at least one recent case of psychosis published in 2013 in the amusingly titled paper: Out of the cupboard and into the clinic.

Nutmeg contains myristicin, a compound related to other hallucinogenic substances, and its effects on the brain are wide-ranging. In mice, nutmeg extract seems to have both antidepressant-like and aphrodisiac effects. (Whether the mice had hallucinations of cheese remains unknown.) Cinnamon and ginger also contain substances chemically related to myrsticin. If taken in large enough doses – definitely not an experiment to try at home – they can sedate, stimulate, or scramble your brain. Ginger even inhibits the same enzyme as a major class of antidepressant drugs, perhaps making gingerbread genuine food for thought.

One spice, however, might improve your mood without too many questionable side effects: as well as flavouring fancy dark chocolates, chilli can produce a guilt-free high. The active ingredient in chilli, capsaicin, binds itself to receptor molecules in our tissues that normally signal pain from overheating. The resulting pain induces the brain to release endorphins, its own built-in painkillers. Since endorphins are in the same chemical family as morphine, they have the same feel-good effect.

That leaves the most important question, that of holiday beverages, till last. While St. Paul did encourage using a little wine for thy stomach’s sake, keeping off the mulled wine for a few months is still a good idea. All those creativity-enhancing spices in combination with alcohol, a well-known depressant, make for a potent brew that might not always be uplifting. But chilli hot chocolate? A perfectly respectable way to alleviate any winter blues, and even if it is only a placebo, it’s a deliciously dark and fiery one. Yum.