Sleep training is one of the most debated topics in parenting. The evidence is more nuanced than either side of the debate suggests - and the right approach depends on your family, your baby's temperament, and what you can sustain consistently.
Gradual retreat
Sit beside the cot and gradually move further away over days or weeks. Your child learns to fall asleep with decreasing input from you. Well-evidenced, gentle, but can take 2-3 weeks.
Controlled checking (controlled crying)
Leave for increasing intervals (2 mins, 5 mins, 10 mins), returning briefly to reassure without picking up. Multiple studies show it's effective and causes no measurable long-term harm. The first few nights are hard.
Responsive settling
Pick up when crying, put down when calm. Repeat. Teaches the child that you're there, but that the cot is where sleep happens. Works well for younger babies.
What the evidence says about harm
Large studies, including a well-known Australian randomised trial with 5-year follow-up, found no difference in emotional health, behaviour, or parent-child attachment between sleep-trained children and controls. The NHS does not endorse or condemn any particular method.
What matters most
Whichever approach you choose, consistency is more important than the method. Switching between approaches confuses your child and extends the process. If one approach doesn't feel right, pick a different one - but give it at least a week before deciding it isn't working.