WTF has happened to my dear, easy to settle, sleep-through-the-night toddler?

[GrassW1dow]

DS is 20 months.
I did sleep training with him at c. 8 months. Since then, he has been an amazing sleeper:

• I put him to bed and leave the room and he is fine. Settles himself to sleep. (well, shouts a bit but nothing that lasts very long).
  

• Sleeps right through the night.
  

It's been like this for over a year. Bliss
And now, since last week, everything has gone to pot He won't fall asleep on his own when I put him to bed, cries hysterically if I leave the room. And he wakes in the night and cries out for someone. And when this happens, again, he won't fall back to sleep on his own.
I am gutted. What has happened and what can I do to try and correct it??
All advice gratefully received.
thanks

[minipie]

Textbook 18 month sleep regression. DD2 was exactly like that.

Happily with DD2 it only lasted a week (maybe 10 days) and then she was back to normal. In the meantime we stayed with her at bedtime till she fell asleep and tried whatever we could to avoid nighttime wake ups - for example a bit of pre emptive calpol if she seemed a bit hot or teethingy.

[LHReturns]

OP could it be a new understanding and fear of the dark and being alone? My DS is older at 27 months, but last week after literally 18 months of zero night waking (a dream sleeper) he decided he didn't want to go to bed. Went absolutely crazy (he is still in a cot). We have worked out it is the dark that he doesn't like (he has expressive speech delay, so can't tell us specifically).

I suppose a natural progression for all toddlers. We have got him a very cool, rainbow colour changing, LED nightlight of a train, and he can control the remote control in his cot.

He is now happy to go to bed again. Could your little boy be scared of something that has never bothered him before?

[Shortfatandangry]

No advice, just as I'm going through the same and have massive sympathy. My health visitor has been great, sympathy wise although we've not had any significant improvement yet. Fingers crossed for us both!

[GrassW1dow]

Hello. Thanks all for the advice.
Short If it gives you hope, DS went down tonight without a squeak!! Hurrah! And last night slept through till 7am....
.....so (and probably tempting fate here), I think it may just be a phase and there aint much you can do about it but sit it out!

[Tippytoes13]

I've been going through the same with my daughter who has just turned 15 months, finally she is beginning to sleep through again, it had been going on for a while, but for me it was a mix of teething, she's cut three molars over the past 7 weeks, she was ill, also we changed her routine, as she was eating to late and also had no real structure to her evening routine. It could be he's scared of the dark, or as someone suggested sleep regression, which I think is very common for toddlers.