Characteristics of the sample

A total of 42 unique patients with ARFID participated in treatment in our program during the study period. Individuals who transitioned from inpatient to outpatient treatment were considered as having one single course of treatment. There were 43 unique courses of treatment: One individual had two courses of treatment, and the remainder (97.6%) were unique. For the individual who attended treatment twice, the most recent course of treatment was used for data analyses. See Table 1 for demographic characteristics of the sample.

Table 1 Demographic characteristics (N = 42)

With respect to demographic characteristics, the gender breakdown of the study sample was diverse, with 61.9% identifying as cisgender women, 21.4% identifying as cisgender men, and 16.7% identifying as transgender, gender non-binary, or another diverse gender identity. The sample ranged in age from 17 to 48 years old, with an average age of 26.0 years (SD = 6.9), and most were single (90.2%). The majority were not employed (68.3%) or enrolled in school (75.6%), and most (76.9%) received some government or other financial support (with more than 40% of the sample fully financially dependent). The majority of the sample had a maximum educational attainment of high school (41.5%) or less than high school (22.0%).

The patients exhibited diverse presentations of the typical ARFID maintaining mechanisms. Of the total sample, 47.6% had the lack of appetite/interest presentation, 57.1% had the sensory sensitivities presentation, and 69.0% had the fear of aversive consequences. The majority (61.9%) exhibited two or more of the maintaining mechanisms. See Table 2 for further details.

Table 2 ARFID maintaining mechanisms in the study sample (N = 42)

Our sample had a diverse array of psychiatric comorbidities, including: Neurodevelopmental disorders (42.9%); mood disorders (52.4%); anxiety disorders (61.9%); obsessive compulsive disorder (16.7%); trauma- and stressor-related disorders (21.4%); somatic symptom disorder (7.1%); substance use disorder (4.8%); and borderline personality disorder (9.5%). A subset of patients (n = 15; 35.7%) were also documented as having one or more comorbid medical condition that may affect food, eating, digestion, or their gastrointestinal system (e.g., Crohn’s disease, Celiac disease, GERD). See Table 3 for further details.

Table 3 Co-occurring psychiatric and medical concerns (N = 42)

Given possible etiological differences for patients with either the lack of appetite/interest of sensory sensitivities mechanisms compared to the fear of aversive consequences mechanism of ARFID [19], we also descriptively examined the rates of neurodevelopmental and anxiety disorders in these two groups (as these concerns may be particularly relevant to understanding possible etiological differences). In the participants with exclusively the lack of appetite and/or sensory sensitivities presentation, 46.2% had neurodevelopmental disorders and 53.8% had anxiety disorders. In contrast, in participants with exclusively the fear of aversive consequences presentation, 25.0% had neurodevelopmental disorders whereas 50.0% had anxiety disorders.

Treatments received

See Fig. 1 for a treatment flow diagram that maps out the patients’ flow through treatment, including completion rates and length of treatment. See Fig. 2 for an additional treatment flow diagram that summarizes pre-treatment clinical variables and post-treatment clinical outcomes (i.e., BMI, EDE Global, CIA, and PCL-5 scores), by treatment type. Note that in Figs. 1 and 2, some of the outpatient treatment cells/results had small sample sizes (i.e., ns = 3 to 4). In these instances, medians and ranges are reported in Fig. 1 and 2 instead of means and standard deviations or percentages (as applicable). Means, standard deviations, and percentages for the combined outpatient groups (i.e., IOP and individual therapy, and reported separately for inpatient transfers to outpatient versus direct entry to outpatient) are presented in the main text as indicated.

Fig. 1

Treatment flow diagram including length of treatment, by treatment type

Fig. 2

Pre-treatment and post-treatment clinical variables, by treatment type

Inpatient treatment

Of the 42 unique patients in the study, 27 (64.3%) received inpatient treatment. Dispositions at end of inpatient treatment for these 27 patients were: eight completed and transitioned to the IOP (29.6% of inpatients); five completed and transitioned to CBT-AR only (18.5% of inpatients); two ended inpatient treatment prematurely and transitioned to outpatient services (i.e., one to CBT-AR only and one to IOP; 2.7% of inpatients); and 12 (44.4%) did not transition to outpatient services. Of the 12 individuals who did not transition to outpatient treatment: two completed inpatient treatment and no further ARFID treatment was recommended; and 10 (37.0% of the total inpatients) were discharged prematurely. Of the 12 patients who ended treatment early (10 patient-initiated and two program-initiated discharges), nine patients had difficulty tolerating the inpatient environment or engaging with treatment and three believed the treatment was not a good fit to their needs.

Of the nine patients who transitioned from inpatient to IOP, eight (88.9%) completed IOP and one (11.1%) ended treatment early. For the six patients who transitioned from inpatient to individual therapy only, three (50.0%) completed CBT-AR, and three (50.0%) ended treatment early. Reasons for withdrawal from the two outpatient services included problems with attendance, competing health concerns that interfered with treatment, and patient belief that they had achieved all their treatment goals prior to the end of the treatment protocol.

Direct entry to outpatient treatment

Fifteen of the 42 unique patients in the study started their course of treatment as outpatients. Three patients (7.1% of the total sample) had a direct entry to IOP, all of whom (100%) completed treatment. Twelve patients (28.6% of the total sample) received individual therapy only. Of these, 11 (91.7%) completed treatment, and one (8.3%) was withdrawn due to low motivation and engagement.

Weight and BMIInpatient treatment

The majority of individuals who were admitted as inpatients (n = 21; 77.8%) were significantly underweight (BMI < 17.5) at admission, with an admission BMI range of 12.0 to 16.7. A paired sample t test showed that for underweight patients who completed inpatient treatment (n = 12), BMI increased significantly from pre- to post-admission, t(11) = -8.91, p < 0.001, with a mean increase of 3.6 (SD = 1.4) BMI points. Underweight patients who completed the recommended course of treatment gained an average of 10.4 (SD = 4.6) kg during inpatient treatment (Length of stay: M = 6.0 weeks [SD = 2.0], Range = 4.0 to 11.0), t(11) = -7.78, p < 0.001.

For patients who were significantly underweight at admission and who transitioned from inpatient treatment to one of the two outpatient treatments (n = 11), the average BMI at the end of outpatient treatment was no longer in the underweight range. BMI at transition to outpatient treatment was M = 18.5 (SD = 0.9; Range = 16.7 to 19.8) and BMI at end of outpatient treatment was M = 19.7 (SD = 1.0; Range = 17.4 to 21.7). A paired sample t test showed that these patients increased an additional 1.21 BMI points during outpatient treatment, t (10) = -3.28, p = 0.008.

Direct entry to outpatient treatment

None of the patients who started treatment as an outpatient were significantly underweight (BMI < 17.5) at baseline. Therefore, BMI change over time was not examined.

Other clinical characteristics“Classic” eating disorder psychopathology

Pre-treatment EDE Global scores were low at baseline for both inpatients (M = 1.02, SD = 0.72, n = 26) and outpatients (M = 0.91, SD = 0.63, n = 15). Both group means were less than one standard deviation from the published mean in a community norm sample of women without eating disorders (i.e., M = 0.932, SD = 0.805, N = 243) [17]. Because baseline EDE global scores were not elevated, post-treatment EDE scores were not examined.

Impairment due to the eating disorder

Pre-treatment CIA global scores exceeded the published cut-off score of 16.0 for inpatients (M = 22.67, SD = 13.76) and outpatients (M = 20.10, SD = 11.61), indicating significant clinical impairment due to the eating disorder [21]. Overall change in CIA scores during treatment (regardless of each patient’s specific treatment trajectory through one or more of the treatments) was examined using a paired samples t test for all patients who had baseline and post-treatment CIA data (n = 28). Over the course of treatment, patients made significant improvements in CIA scores, t(27) = 3.19, p = 0.004. The overall mean decreased from 20.38 (SD = 12.37) at baseline to 12.49 (SD = 12.86) at end-of-treatment, and 71.4% were below the threshold for clinically significant impairment.

Current trauma-related symptoms

Seventeen patients (40.5% of the sample) screened positive for PTSD at baseline using the PCL-5 (37.0% of the inpatient group and 46.7% of the outpatient group). Mean PCL-5 scores for those who reported a DSM-5 criterion A trauma were M = 41.00 (SD = 20.75, n = 11) for inpatients and M = 46.50 (SD = 15.76, n = 6) for outpatients. These scores reflect high levels of PTSD symptom severity.