Dear Tanya,

My daughter is 22 months old. She was induced 21/2 weeks early as she wasn't growing properly (insufficient fluid), she had reflux as a baby and didn't start eating solids until almost a year (she couldn't physically swallow the food, as her muscles had not developed enough). All this meant that until 13 months she would wake at least two or three times a night in discomfort and, later on, from hunger.

Once she was eating sufficiently, we cut down on the night-time milks, but she then developed a heavy cold, so the night waking continued. Through controlled crying, we eventually got her to settle on her own and sleep through the night to 5.30am, which we could cope with. But this has started to creep back to 4am. We go in and tell her it's night-time and to lie down but she is standing up, wide awake and screaming - and she has done an eight to nine-hour stretch. (She goes to bed at 7.30pm and we try to get her to sleep during the day, morning always, for 45 mins-11/2 hours max. She wakes up herself).

Problem: if we leave her (which we have tried a number of times), she wakes up her older brother, who then can't get back to sleep. So we take her into our room and usually give her milk and hope that she goes back to sleep for an hour or so. Sometimes, however, she is too lively to go back to sleep. We are exhausted (we both work). Incidentally, my daughter is small, on the ninth centile, and the 4am-ish milk replaces what would ideally be her 6-7am milk. Could she just be small and therefore in need of milk earlier than some other children (ie, little and often)?

My sister shows little interest in my welfare

A reader who feels that she provides her sibling with a lot of support but receives little back asks our expert for advice

BACKGROUND

• My six-year-old daughter has hairy legs

• Our daughter won't go to school

• How to break the despairing cycle of self-harm

• I cringe when my son touches me

• Why is my teenage son so abusive to me?

Daniel

I always feel really sorry for parents of children with sleep problems because disrupted and insufficient sleep for both adults and children can have bad effects on so many aspects of life - relationships, behaviour, work. I was hopeless at managing the sleep of my eldest, Lily, when she was a baby, much to my husband's despair (“But you've written books about this,” he would exclaim as I stood over her cot sobbing at 4am). Against all my academic and clinical training, I would lift Lily and rock her back to sleep or even bring her into my bed. There's something about our little ones seeming vulnerable and alone in the dark at night that makes boundary setting even more difficult.

It is important not to underestimate the impact of prolonged sleep problems on families. I have worked with couples who are on the brink of separation after months, even years, of sleepless nights that have become times of immense rows. Having an intimate relationship is difficult when exhausted, and impossible when a small person is wedged in between you.

There are parents who, for cultural or ideological reasons, share their beds with their young children and this can work for all concerned. Therefore the first issue is to decide what sleeping arrangement would best suit your family and then work towards it. Given that you are probably also pretty tired as you read this, I shall attempt to unravel the complexities systematically.

First, if children are not getting enough sleep they are likely to develop problems with concentration, attention and overall behaviour. At 22 months your daughter should be hitting around 12 hours' total sleep which comprises naps plus all night-time sleep. I suspect that she already has a sleep debt and, as with mastering any skill when exhausted, learning how to sleep through the night will be very difficult for her and a real challenge for you to teach her.

Secondly, it is common for parents of children who have had a rather early entry to the world, followed by sickly behaviour or even illness, to find sleep training very challenging. Often this seems to be because at night-time, when there is a period of separation from our little ones, parents of children who have been ill will often respond to any small cry with anxiety. This often centres on concern that there is something wrong with the child and so a pattern of checking and responding to any night-time noi- ses is set up. Thirdly, many parents like you will cease to sleep-train their child robustly because they are concerned that siblings are woken.

Finally, and most importantly, parents of “small” children, especially those with feeding difficulties, will get anxious and confused by their child's waking behaviour and presume that it is related to hunger, and so feed with bottles throughout the night. In fact, your daughter wakes because she needs the feed to help her to sleep rather than waking because she needs to feed per se - a subtle but extremely important difference.

Here is the approach I propose for you. First, some maths - look at a 12-hour sleep total for your daughter and calculate it backwards from morning wake time. Therefore if you want a 6.30am wake time and an hour of sleep in the day, her bedtime would be around 7.30pm. Work towards this by being rigorous about naps and waking if she sleeps more than an hour in the day.

Her entry into the world 22 months ago was sudden and fraught with health concerns. But you must separate that vulnerable infant from your now healthy and robust toddler. Being on the ninth centile makes her the ninth biggest (or 91st smallest) of 100 children of her age, but this is still within the normal range and her consistent small size is not related to her being underfed if all other developmental milestones are being achieved.

The problem is that she requires a feed to get back to sleep and may therefore take some of her calories at night. To bump her out of this you will need to stop the feeding at night and increase her daily calorific intake. If controlled crying and a more “cold turkey” approach seems too harsh, replace the milk with water and then reduce over successive nights. Also, to increase her daily calorie intake, don't give her a huge bottle of milk when she wakes as it will reduce the amount of food that she eats at breakfast. Given that your daughter may not like this and protest at first, you should not worry too much about your son waking. If he does, try to get him back to sleep or put him in your bed until sleep training is done.

If controlled crying worked before, it will work again, although I am not a huge fan of the “leave them for as long as it takes” method. It has been suggested that excessively prolonged crying in little ones leaves them with increased stress levels. A gradual approach of leaving them for increasing five-minute increments with a brief reassurance between each (a vague “shh” and a small pat and then leave) will be enough up to a maximum of 15 minutes (a total of 30 minutes of crying: 5 + 10 + 15 = 30). After that you can check during shorter spells of crying. There are those childcare writers who advocate leaving babies and toddlers to cry without any checking for as long as it takes. Many of them have not had children of their own and I know as a parent of two that what works theoretically for parent and child and what works emotionally for them are often different. Taken together and done consistently, these approaches should give success in under two weeks, if not sooner.

I wish you all sweet dreams soon!

If you have a family problem, e-mail Dr Tanya Byron.

Times recommends

• It is possible to look stylish while pregnant
• Britain’s tot models
• Who and what benefits from the heat wave?