Remember when, as a child, you were astonished to discover that not only did your teacher not retreat to the resources cupboard to charge overnight, but that they had a life outside work and even a family? Some adults still seem not to have grasped this about MPs.

Last night, Labour MP Luciana Berger posted a thread on Twitter in which she justified not attending a rally for the NHS's 70th birthday in London at the weekend. It was quite a lengthy thread, in which Berger set out all the NHS-related work she had done that week, and rather plaintively said that while also knocking on doors over the weekend in Liverpool, 'I also spent some precious time catching up with my partner and 1 year old daughter'. Why bother setting out what sounds like a perfectly acceptable working week with a bit of family time thrown in? Well, Berger was receiving a barrage of tweets criticising her for not turning up, and she clearly felt somewhat stung by the criticism. Naturally, this being Twitter, her posts didn't cause everyone to rethink their position, with some charming posters then suggesting she would have turned up had the event been organised by her 'faction' or by Labour Friends of Israel.

This goes a bit further than the usual impossible expectations on MPs to turn up to everything in different parts of the country at the same time. You're damned if you're at a constituency event rather than in the House of Commons Chamber, and you're damned if you cannot possibly get between the two. You're also damned if you want to spend time with your family like a normal person, and damned by the statistics around marital breakdown in Parliament, without any thought that the two things might possibly be connected. But that's normal, that's been going on for years before Twitter.

What's new is that MPs are - I think - being driven slowly mad by Twitter. It has become a much noisier version of the below-the-line thread of comments on newspaper sites, the realm of angry obsessives who rarely read the piece or notice what the politician in question is actually up to before posting a torrent of unpleasantness.

Berger knows better than any of us the difference between abuse and unpleasantness: people have been jailed for sending her the most disgusting threats and abuse, many of them deeply anti-semitic. But the non-abusive unpleasantness, the constant suggestions that you are useless, stupid, letting everyone down and not good enough can have a serious effect on parliamentarians too. One MP told me that she had started to believe what tweeters were saying about her. I often notice MPs replying to tweets between 10pm and midnight, presumably when they are lying in bed and when they should be trying to get to sleep. Instead, they're engaged in a late-night stand-off with someone who they've never met, who may actually be a paid Russian troll, or who is working out their own sense of inadequacy by sneering endlessly at others.

It's something that the Parliamentary Health and Wellbeing Service is increasingly worried about, as nearly every MP who seeks help for their mental health (a very high number) cites social media when listing the problems that have made them ill. I understand that the wellbeing staff are advising MPs to withdraw from the social media site as much as possible, telling them that it's the equivalent of dipping their private parts in honey and exposing them to angry bees.

Some might say that MPs should be thick-skinned enough to shrug this stuff off, but I'm not so sure that our democracy would benefit from having more people in it who don't care whether they are doing a good job and who ignore criticism. Similarly, thick skins don't always make for good constituency MPs: you need a fair bit of emotional intelligence to get through a surgery packed with people whose lives have been totally messed up and who need your help. Others might argue that MPs shouldn't go on Twitter at all, which sounds simple enough, but is quite difficult given it's the modern coffee house where news and debate first appear.

But there is a danger, not just that MPs' own mental health will suffer as a result of the endless unpleasantness pouring out of their phones and into their beds or sitting rooms or rare family moments, but also that they become more sensitive to Twitter than they are to the rest of their constituency, or Parliament. Constantly conducting yourself in a way that means you hope the trolls will leave you alone for a bit means you self-censor, or avoid doing certain things that might be right but will leave you with waterfalls of online abuse.

What can MPs do? A few now only post on their Twitter feeds, but don't read their replies. Some leave the site with a grand announcement, only to creep back a few weeks later. Of course, they could hope that suddenly people learn to behave with at least the same level of decorum that you'd expect in face-to-face contact. But that's not going to happen overnight. A good first step might be a general recognition in politics that Twitter, once a forum for debate and humour, has become a malign force that should be treated with caution. Stepping back from it will only mean MPs lose touch with a group of people who seem to think that obsessive unpleasantness and a refusal to engage reasonably are entirely justifiable. It may put them back in touch with those who can provide the sort of criticism that will make a parliamentarian a better servant of the people, rather than someone who believes that they are in fact useless.