What side effect is most commonly associated with corticosteroid use?

Weight gain is a common side effect associated with corticosteroid use due to several factors related to the pharmacological effects of these medications. Corticosteroids, especially when used long-term, can lead to increased appetite, fluid retention, and changes in metabolism that promote fat accumulation. This weight gain is often more pronounced in areas like the face, abdomen, and back of the neck, leading to a characteristic appearance known as "moon facies." Additionally, corticosteroids can influence hormonal balances and increase the deposition of adipose tissue.

In contrast, while nausea, insomnia, and diarrhea can occur with corticosteroid use, they are not as prevalent or as directly resulting from the medication's primary effects as weight gain. Nausea is often more associated with other medications or underlying conditions treated with corticosteroids. Insomnia might arise from corticosteroid-induced stimulation or changes in mood, but it is not as universally experienced as the weight-related side effects. Diarrhea may occur due to gastrointestinal side effects but is not a common or typical reaction to corticosteroids. Therefore, the tendency for weight gain stands out as the most significant and frequent side effect associated with corticosteroid therapy.