It's often difficult to identify the exact cause of constipation. However, there are a number of things that contribute to the condition, including: not eating enough fibre, such as fruit, vegetables and cereals a change in your routine or lifestyle, such as a change in your eating habits ignoring the urge to pass stools side effects of certain medications not drinking enough fluids anxiety or depression In children, poor diet, fear about using the toilet and problems toilet training can all lead to constipation.