If scientists wrote horoscopes, this is what yours would say

Martha Gill's Irrational Animals column.

A new year, a new set of horoscopes, a renewed chorus from naysayers who fail to see the link between when they were born and what will happen to them next Tuesday. But science says they’re just not looking hard enough. Tiny seasonal variations at your time of birth can affect both your health and your character. Finally – here’s a horoscope based on real medical evidence.

Aries: 21 March – 19 April
You’ve never been that bright, Aries, and medics at Indiana University put this down to a heightened use of pesticides around the time of your birth. You also sometimes feel that you’re sleepwalking through life. Give in to the feeling – it’s just narcolepsy (more likely in those born in March or April).

Taurus: 20 April – 20 May
Oh, Taurus, sometimes you’re on top of the world, other times you just can’t get out of bed. Your friends are confused: what’s going on? Tell them that babies born in May are happier – they first experienced the world in summer. They are also more likely to suffer from seasonal affective disorder; depression hits in the darker months.

Gemini: 21 May – 21 June
Children born at this time are often better behaved and less likely to play truant. Maybe it’s time to let loose a bit, Gemini.

Cancer: 22 June – 22 July
Cancerians, you usually think yourselves lucky – due to low rates of postnatal depression in mothers of summer babies. Your instincts are off, however: you’re at a slightly higher risk of Hodgkin’s lymphoma, according to Danish research from 2003.

Leo: 23 July – 22 August
Your friends tell you you’re just not the maternal type. They’re right: Austrian research finds that those born now grow up to have the fewest children.

Virgo: 23 August – 22 September
You keep telling people you’re big-boned but they don’t believe you. It’s true, though – your mother got more sunlight as her pregnancy progressed and the Vitamin D gave you thick, strong bones. See?

Libra: 23 September – 22 October
Librans, you have the best chance of becoming a professional footballer. You’ll be one of the biggest children in the school year and get picked for the best team early on. Things will progress from there. Hurray for Jupiter in the ascendant or whatever.

Scorpio: 23 October – 21 November
This year is as good a time as any to take up yoga, because you’ll be feeling flexible and energetic, partly because of your low risk of arthritis and multiple sclerosis (as your mother got plenty of sunlight late in her pregnancy).

Sagittarius: 22 November – 21 December
Sagittarians like to live life at the sharp end – December babies are the most likely to become dentists. But take off those plastic gloves and have a rest in the chair: cold temperatures at birth increased your risk of eczema and heart disease.

Capricorn: 22 December – 19 January
Capricornians, you are clever, tall and successful – your mother was pregnant in the summer and ate lots of fruit and vegetables. If you have one flaw, it’s that irritating tendency to have epilepsy, caused by prenatal winter infections.

Aquarius: 20 January – 18 February
This year, you’ll be as clearsighted as ever; low levels of daylight at birth gave you better long-distance vision. Older Aquarians may be feeling under the weather, though – an early lack of Vitamin D has been linked to depression later in life.

Pisces: 19 February – 20 March
Assertive, successful, bossy: there are more CEOs born now than at any other time of the year. Male Pisceans beware: you’re at a marginally higher risk of autism.