I found explicit photos of my boyfriend and his ex and I felt sick... because she was so unattractive. I'm one of thousands struggling with 'Rebecca Syndrome'

It’s 2am and I’m home alone, falling down a rabbit hole online. On my phone is the Instagram profile of a new man I’m seeing, and I’m forensically looking through it for evidence of his past love life.

There are holiday photos, party photos, weekend-away photos. And in all of them, I hunt for ‘her’ – the one before me... and the ones before that. My thumb hovers over each, making sure not to inadvertently hit the ‘like’ button that would alert him to my nocturnal snooping.

When I was younger, and people were less prudent about what they shared online, there would be years’ worth of these images to torture myself with, my new boyfriend smiling with his arm around another woman.

Now I’m in my 30s, and most have us have wised up a bit about the wisdom of documenting every moment of our lives on social media, I have to look harder for evidence of girlfriends past. They might be within a group shot, or silhouetted in the distance – who’s that riding the bike in front of him? – but they’ll still be there.

Lucy Holden talks to a psychoanalyst about what might be behind her obsessional Instagram scrolling to find out about her new man's exes

Lucy Holden talks to a psychoanalyst about what might be behind her obsessional Instagram scrolling to find out about her new man's exes

Armie Hammer, left, and Lily James in the film Rebecca. The term Rebecca Syndrome is derived from the 1938 novel by Daphne du Maurier on which the film is based

Armie Hammer, left, and Lily James in the film Rebecca. The term Rebecca Syndrome is derived from the 1938 novel by Daphne du Maurier on which the film is based

Lily James as Mrs de Winter in the movie Rebecca, which tells the story of woman who marries a widower but discovers that her new home is haunted by the memory of his dead wife

Lily James as Mrs de Winter in the movie Rebecca, which tells the story of woman who marries a widower but discovers that her new home is haunted by the memory of his dead wife

I’m rational enough (even when doing such an irrational thing) to know comparing myself to past girlfriends is utterly pointless. But when you know next to nothing about his exes, it’s only natural to wonder what’s not being said.

Was the previous ‘me’ a Heidi Klum type who’d started her own charity and ran ultra-marathons for fun? Maybe she was a philanthropist doctor who didn’t struggle to only drink at the weekends.

Whoever she, or rather they, were, I can’t help but imagine it all to be more impressive than what I have to offer. So I take to social media looking for concrete evidence I hope will somehow validate me.

Now this habit has a catchy new name: Rebecca Syndrome.

Also known as retroactive jealousy, the term comes from the 1938 Daphne du Maurier novel, in which a young woman marries a widower but soon discovers that her new home is haunted by the memory of his dead wife, Rebecca. The second Mrs de Winter becomes obsessed with the lingering presence of her predecessor.

How much worse it is now, in the age of social media. Today, all a new lover and his ex need are public Instagram accounts for a wealth of intel to be available. And once you find her account, it’s impossible not to compare yourself to her.

Psychoanalyst Toby Ingham has written a book on the phenomenon: Retroactive Jealousy, Making Sense of It. He says: ‘Why would anyone like to think of their partner as having had previous partners?

‘Rebecca Syndrome is an obsessional problem and my belief is that it’s caused by attachment issues that are older than the current love relationship and are being brought back to life.’

That made me think. I’m pretty sure my feelings of doubt in relationships come from the fact that I don’t expect any of them to last. But why? I’ve had a lot of relationships, but I’ve left them as many times as I’ve been left.

Possibly that’s because I don’t know what I want, so look for an excuse to call it off. Or perhaps my attachment issues are connected to the fact we moved around when I was very young and I got used to people I liked being left behind. Better to leave first, eh?

The film Rebecca, starring Armie Hammer and Lily James, tells the story of how a young woman becomes obsessed with the lingering presence of her husband's first wife

The film Rebecca, starring Armie Hammer and Lily James, tells the story of how a young woman becomes obsessed with the lingering presence of her husband's first wife

Obsessional scrolling to find out about a new man's exes may be caused by attachment issues from a person's past that are being brought back to life in the present

Obsessional scrolling to find out about a new man's exes may be caused by attachment issues from a person's past that are being brought back to life in the present

But there could be more recent explanations for my ‘retroactive jealousy’. When I was 26, I was seeing a married man who claimed to be separating from his wife, telling me he’d already moved out of the family home. That turned out to be a lie – and a bit of me still wonders why I didn’t try harder to uncover it. Why didn’t I do my homework online?

Maybe his (still) wife feels the same, because I woke up not long ago to find she’d requested to follow me on Instagram – presumably a dreaded slip of the finger whilst on my profile very late at night, because when I checked the account, the request had already been cancelled. Cringe. But it could happen to any of us.

The problem is that you can’t win, whatever you find. I once found explicit photos from a previous relationship on a boyfriend’s computer – and the thing I remember feeling so sick about first was that the girl wasn’t massively attractive. If she’d been much more attractive than me, I’d have felt awful, so why did the fact she was less attractive make me feel horrendous, too? Perhaps it’s a sign that I’m not all that attractive either?

Rebecca Syndrome taints a new relationship in many subtle ways. Holiday photos are a particular low point; you know you won’t want to go to Malta or the Amalfi Coast if he’s already had an amazing time there. Then you realise you’re looking at a wedding they attended together in 2017 and suddenly feel quite sick. Did they once think they were going to get married? Did he wish they had?

I know this digital detective work may sound extreme. But for those of us who have lived a sizeable chunk of our lives online, it’s par for the course – not to mention far less fraught than subjecting your new beau to a verbal interrogation about his past loves.

No matter how common Rebecca Syndrome is, it’s still unhealthy, insists Ingham.

‘We never see the kind of emotional insecurity that dating involves coming, and that is of course completely exacerbated by modern technology in which we can see what our partner ‘likes’ on social media, or if they’re still friends with an ex.

‘Before they know it, people with obsessional problems become locked into an introspective loop.’

‘Cyber stalking is the pits,’ agrees my friend Lottie, 34. ‘Not only does it make you feel like a psychopath, but it ruins the beginning of any relationship.

‘I don’t feel like a jealous person, so why can’t I resist looking at someone’s past online? Even my sister, who’s now had a baby and is married, does it.’

Another friend takes a more extreme view: ‘If men weren’t so untrustworthy then the pressure wouldn’t be on us to try and do the due diligence,’ she says.

‘There’s nothing worse than being surprised with a “I’m getting back with my ex” chat. And if someone’s Instagram is full of recent photos of them together, that’s a huge red flag for me.’

Of course, I’ve dated enough jealous men to know cyber-stalking is a male problem, too – and that it can easily feed into something far more toxic. I’ve had controlling boyfriends who have hacked my email, stolen my phone and made me go through entire relationship histories to ‘make them feel better’ (which it never does, of course).

Adding fuel to the fire is the fact that we tend to document only our best moments on social media, curating an enviable version of a relationship that may, in reality, be far from perfect.

At the end of Du Maurier’s novel, the illusions come crashing down. We discover that glamorous, captivating Rebecca was actually awful. Malevolent, ‘wicked’ and adulterous, she died pregnant with another man’s child.

It’s a denouement I’ll try to remember when I next find myself staring at a man’s loved-up posts with his ex. After all, they broke up, didn’t they?