Behaviour Changes in Babies

One of the first signs of illness in babies is a change in behaviour. The baby may cry more or have a change in activity level. Generally, if your baby is active when awake, feeding well, and can be comforted when crying, small differences in activity level or crying are normal. However, if your baby becomes lethargic or irritable, it may be time to see a doctor. Lethargy or irritability may be signs that an illness is present.


Lethargic or listless babies have little or no energy. They sleep longer than normal, and they may be difficult to wake for feedings. When awake, they are drowsy or sluggish; they are not alert and they do not pay attention to visual stimulation or sounds. Lethargy can develop slowly over time, and parents may have difficulty recognizing it.

Lethargy may be a sign of a common infection such as a cold, or a serious type of infection such as influenza or meningitis. Lethargy can be caused by heart conditions or blood diseases such as thalassemia. There are numerous other conditions that can cause lethargy, and lethargy is usually one of many symptoms associated with any particular condition. Therefore, if you notice that your baby is particularly lethargic or listless, bring him to the doctor for an examination. Treatment will depend on the particular condition that is making your baby lethargic and listless.


Crying is a baby’s only way of communicating. Over time, babies develop different cries depending on what they need: food, sleep, a diaper change, or a cuddle. Parents gradually learn to decipher their baby’s cries and respond accordingly. Usually parents can console their baby by providing what he needs and cuddling him. However, some babies may begin to cry inconsolably. This may be due to a condition called colic, where babies may cry non-stop for three hours or so each evening. Colic begins shortly after birth and may continue for the first six weeks of life.

A baby who becomes very irritable, fretful, and fussy, with long crying periods, may be ill or in pain. The baby may also become quite jittery or start to tremble. Irritability may be a sign that your baby has constipation, abdominal pain, an earache, or a viral or bacterial infection. The cause of your baby’s irritability may simply be constipation but it might be something more serious. If your baby is irritable and continues to cry longer than normal, bring him to the doctor for an examination. Treatment will depend on the particular condition that is making your baby irritable.

Hazel Pleasants, RN, MN

Andrew James, MBChB, FRACP, FRCPC