Citalopram was initiated at 10 mg daily for one week, with dosage increased to 20 mg daily during week 2, with an optional increase to 40 mg daily at week 4 or thereafter if response was judged to be suboptimal (CGI-I or CGI-S > 2).

Placebo administered in capsules identical to those containing citalopram using microcrystalline cellulose.

Participants will be randomly assigned to citalopram or placebo in a parallel groups design for 8 weeks of double-blind treatment beginning with 10 mg per day week 1, 20 mg per day week 2, and 40 mg per day week 4 or thereafter if response is suboptimal and there are no significant side effects.

Clinical Global Impression Scale - Improvement (CGI-I) is a 7-point scale, with lower values being more favorable, used to assess overall global illness improvement. The CGI is a clinician-completed measure, with values ranging from 1 (very much improved), 2 (much improved), 3 (minimally improved), 4 (no change), 5 (minimally worse), 6 (much worse), to 7 (very much worse). CGI-I scores of 1 (very much improved) or 2 (much improved) were considered to indicate an acceptable treatment response. A global measure of functional status was chosen as a primary outcome due to the broad array of symptomatology seen in pediatric RAP and the ambiguous relationship between functional status and symptoms of pain, anxiety, and depression in pediatric RAP. The CGI-I is a dichotomous primary outcome measure of global clinical improvement with clinical response be defined as a CGI-I score of 1 or 2 for at least two consecutive weeks.

Clinical Global Impression Scale - Severity (CGI-S) is a 7-point scale is a clinician-completed measure that requires the clinician to rate the severity of the patient's illness at the time of assessment relative to the clinician's past experience with patients who have the same diagnosis. Considering total clinical experience, a patient is assessed on severity of illness at the time of rating, with values ranging from 1 (normal, not at all ill), 2 (borderline ill), 3 (mildly ill), 4 (moderately ill), 5 (markedly ill), 6 (severely ill), to 7 (extremely ill).

The API is a well-validated and reliable measure of abdominal pain assessing the frequency, duration, and intensity of abdominal pain consisting of five items assessing the frequency, duration, and intensity of abdominal pain experienced during the prior 2 weeks. Two of the items are scored from 0 to 5, one is scaled 0 to 8, and two are scaled 0 to 10, with lower scores considered to be better than higher scores. Item scores are standardized using Z-scores and then summed to yield an index of abdominal pain that has been sensitive to change in previous epidemiological and treatment studies of FAP. Alpha reliability ranged from 0.80 to 0.93. The API will be a continuous primary outcome measure of abdominal pain.

Pediatric Anxiety Rating Scale (PARS) is a clinician administered measure of anxiety in children and adolescents. The PARS is comprised of a 50-item symptom checklist used to determine the presence or absence of specific anxiety symptoms during the prior week and 7 severity/impairment items, each scored from 0 to 5 . The the score on the 7 items allows the clinician to rate symptom severity and associated impairment on a range from 0 to 35, with higher scores reflecting greater symptom severity and associated impairment. The PARS is characterized by high interrater reliability (ICC = 0.97), adequate internal consistency (α = 0.64), and fair test-retest reliability (ICC = 0.55). There is preliminary support for convergent and divergent validity, and the PARS has demonstrated sensitivity to treatment effects in previously conducted clinical trials.

This double blind, placebo-controlled trial randomized 81 subjects ages 7 to 18 years in parallel groups to citalopram (n=40) or placebo (n=41) for 8 weeks. Citalopram was initiated at 10 mg per day week 1, 20 mg per day week 2, and 40 mg per day week 4 or thereafter if response was suboptimal and there were no significant side effects. Subjects were recruited by clinical referral from both the primary care and specialty pediatric gastroenterology clinical settings. In addition to meeting criteria for FAP, subjects were required to be significantly impaired as reflected by a score of less than 70 on the Children's Global Assessment Scale (CGAS). Potential subjects with physical disease responsible for the observed abdominal pain, eating disorder, bipolar disorder, psychosis, alcohol/drug abuse, intellectual disability (IQ < 70), pregnancy, or prior trial of SSRI antidepressant or venlafaxine were excluded.

Clinical Global Impression Scale - Improvement (CGI-I) is a 7-point scale, with lower values being more favorable, used to assess overall global illness improvement. The CGI is a clinician-completed measure, with values ranging from 1 (very much improved), 2 (much improved), 3 (minimally improved), 4 (no change), 5 (minimally worse), 6 (much worse), to 7 (very much worse). CGI-I scores of 1 (very much improved) or 2 (much improved) were considered to indicate an acceptable treatment response. A global measure of functional status was chosen as a primary outcome due to the broad array of symptomatology seen in pediatric RAP and the ambiguous relationship between functional status and symptoms of pain, anxiety, and depression in pediatric RAP. The CGI-I is a dichotomous primary outcome measure of global clinical improvement with clinical response be defined as a CGI-I score of 1 or 2 for at least two consecutive weeks.

Analysis week 8

Citlaopram: Participants were randomly assigned to citalopram or placebo in a parallel groups design for 8 weeks of double-blind treatment beginning with 10 mg per day week 1, 20 mg per day week 2, and 40 mg per day week 4 or thereafter if response was suboptimal and there were no significant side effects.