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240 Chapter 11 to treatment are based on the observation that their children have been using laxative treatment for a long duration of time, which has led parents to believe their children are dependent on their medication and will require treatment for an extensive period of time, which may be worrisome to them. These beliefs may be reinforced by the observation that skipping one or more doses results in a relapse of symptoms. This could potentially explain why both concerns about medication and a higher importance attributed to medication in controlling symptoms were reported in nonadherent children. In the current study, we used the MARS-5 to assess treatment adherence. Assessment of treatment adherence in children using laxatives is challenging and the method that we used is not ideal. Most importantly, it does not objectively measure the exact intake of medication and therefore only is a derivative measure of adherence. 43 Previous studies in children with asthma have used electronic devices which enabled monitoring the use of inhaled corticosteroids, logging the date and time of each dose administration. 12,13 Currently, such an electronical device is not available for polyethylene glycol treatment monitoring and methods to objectively monitor treatment adherence are needed. In an attempt to overcome this issue, in addition to the MARS-5, we asked patients to fill out a 1-week medication diary to acquire a more direct measure of treatment adherence. Although not all medication diaries were returned, we found an extremely high adherence rate among participants who returned these diaries; 94% of children reportedly took ≥80% of their prescribed medication dosages and 88% were fully compliant with the prescribed treatment. This high reported adherence rate should be interpreted with caution. These results are at risk of selection bias, it is possible that adherent families were more likely to return these diaries. The high adherence rate may also be explained by the short time period the diary was kept. Moreover, keeping a daily diary may help as a reminder to administer a child’s medication, resulting in a higher adherence rate. Furthermore, the results obtained with these diaries are likely at risk of desirability bias. The use of an electronic diary should be considered in future studies, since this enables logging of date and time of data entry. However, it will remain difficult to ensure that data entered into the electronic diary indeed correspond with actual intake of the medication. Another difficulty with the MARS-5 is the cutoff value used for dichotomization, which has varied between studies. 11,17,22–33 In our study, we adhered to the most commonly used cut-off value of 23 and higher, which has also been used in pediatric studies on asthma treatment adherence. 11,17,26–30 However, if a lower MARS-5 score would have been used as cutoff value for dichotomization (e.g. a cutoff value of 21 or 22), the adherence rate in our study would have been higher. It could be argued that laxative treatment, unlike inhaled corticosteroids in the treatment of asthma, is a type of maintenance treatment where dosage adjustments are more acceptable if they