It is often reported that the World Cup dents productivity, either by distracting people from their work or by causing them to be so tired or hungover the next day that they don't turn up to do any. In truth, this is probably overestimated. For instance, it is difficult to know whether people work harder before and after a match in order to make up lost time. There's an incentive to overestimate the effect too – because companies love using spurious research about the World Cup to get themselves talked about. (The productivity of the PR industry rockets every fourth summer, I am sure.) Many other World Cup side-effects, however, do seem to be real.

We use a lot more electricity 

This is not an urban myth. The National Grid really is put under more strain following England's World Cup matches than at any other time. Indeed, the largest sudden spike in electricity consumption ever recorded in the UK – 2,800 megawatts – came immediately after Chris Waddle's penalty sailed over the West German goal in 1990s semi-final.

The effect is caused by millions of people doing nothing besides watching TV, and then at the same time suddenly returning to their electrical appliances. Kettles are usually said to be the main culprit, as the nation consoles itself in a collective cup of tea, and this seems a good guess as kettles do use a lot of electricity. Even so, it would have taken 1.1m kettles to produce the surge in 1990.

This year, the National Grid estimates that the largest foreseeable spike will come at about 8.50pm this evening – half-time during England v Uruguay. It should be only around 1,300 megawatts, which is approximately one large gas-fired power station going at full blast.

We get more violent – even if we win

Football lovers don't only drink tea. Alcohol consumption also rises during the big matches of a World Cup, and violence rises with it. That seems to be the most likely explanation for the fact that police callouts to incidents of domestic violence rise by more than a third after England lose a match, but also rise more than a quarter after they win. Being in a bad mood, in short, is not all of the problem.

Last time, in 2010, 15 British hospitals recorded an average rise of 37.5% in A&E admissions due to assault during the World Cup. Alcohol-related arrests in central Manchester in June have consistently been higher during even-numbered years, when there's a World Cup or European Championship. This may be a distinctly British problem. In Uruguay, a recent study found that property crime falls when the national team is playing – perhaps because everyone is simply too busy watching. Indeed, this year police around the UK have taken the correlation seriously enough to warn known violent offenders before the tournament, and to assemble special callout teams for matchdays.

We have more heart attacks – especially if it's a good game

Do important football matches trigger heart attacks? That may depend on how the game goes. On the day that France won the World Cup in 1998, the rate of heart attacks in that country fell sharply. A few days earlier, however, when England lost to Argentina on penalties, admissions for acute myocardial infarction at English hospitals rose 25% compared to normal, and continued for the following two days.

That said, quite a bit of other research suggests that exciting matches generally can be dangerous – and England v Argentina was certainly a more exciting match than the 1998 final. In Switzerland in 2002, the rate of heart attacks rose 60% overall during the tournament. Perhaps most tellingly, the proportion of men suffering from them rose too. And in 2006, German researchers claimed to find such a strong and clear effect during big matches that they considered them a health risk. "Viewing a stressful soccer match more than doubles the risk of an acute cardiovascular event," the study concluded. "In view of this excess risk, particularly in men with known coronary heart disease, preventive measures are urgently needed." In short: if you have a heart condition, support San Marino.

The stock markets might tumble

If you have money in the London Stock Exchange, you might want to put it into gold, ideally now. Because research by Alex Edmans, a professor of finance at the London Business School, suggests that markets suffer little crashes the day after their national team is knocked out of a major football tournament.

"I investigated the link between 1,100 international football matches and stock returns in 39 countries," Edmans writes. "Being eliminated from the World Cup leads to the national market falling by 0.5% on the next day – controlling for everything else that might drive stock returns. Applied to the UK stock market, this translates into £10bn wiped off the market in a single day."

The effect that Edmans noticed is more pronounced with World Cup eliminations than those in European Championships, and in knockout games more than in the group stage. About half of the value lost comes back shortly afterwards, but the rest is lost for ever. Nor is there any noticeable gain when the team wins. That said, you might get lucky if traders can't be bothered to push your own stocks downwards. Other research suggests a fall in trading volumes around the world during a World Cup, as the markets' attention simply drifts elsewhere.

We have more babies in nine months' time

We don't really need the help of statisticians to prove that people are more likely to start a pregnancy when they are in the right kind of mood – cheerful, optimistic, maybe a little drunk. Legend has it that small baby booms rippled through England nine months after the 1966 and 1970 World Cups, and they are often reported in other countries too. Germany is said to have experienced a 10-15% spike in births as a result of hosting the World Cup during the hot summer of 2006.

Last year, some jovial research in the British Medical Journal also suggested that the legend may have some substance to it. For a long time it had been rumoured that Andrés Iniesta's goal for Barcelona in the 2009 Champions League semi-finals had caused a 45% baby boom in Catalonia. That is probably an exaggeration, but the research did find a statistically significant rise of 16% at two Catalan medical centres nine months after the match. "The heightened euphoria following a victory can cultivate hedonic sensations that result in intimate celebrations," the paper explained, not quite with a straight face. If England do well in Brazil, therefore, we might experience a small boom next spring. Or, to put it another way, we won't.