Introduction

Food addiction (FA) refers to a condition characterized by addiction in relation to some high-fat and high-carbohydrate foods that leads to clinically significant impairment or distress on several areas of functioning [1]. It describes a particular form of uncontrolled eating that is thought to have both behavioral and neurobiological similarities with similar patterns of neural activation as observed in substance use disorders (SUDs) [2, 3].

When analyzing any form of addiction, it is important to look into the cause. In the case of behavioral addiction, the dependence does not involve any substance. Behavioral addiction regards an action rather than a chemical dependency, while in substance addiction, the ingestion of a psychoactive substance is present [4, 5].

The FA has not been formally included in any classification of mental disorders, but the concept was initially developed considering it as an addictive behavior that deserved its inclusion among the substance-related disorders (SRD) in DSM-IV-TR [6]. More recently, researchers in the field of eating disorders (EDs) have claimed that FA should be comprised within the spectrum of ED [7,8,9].

The Yale Food Addiction Scale (YFAS) [10] was developed in an attempt to shed light on the controversial discussion about the concept of FA and to provide a standardized measurement of this pathological behavior according to the diagnostic criteria for substance dependence of DSM-IV. As DSM-5 [11] introduced important changes for the diagnosis of substance-related and addictive disorders (SRAD), the authors created an updated version of this test 7 years later, the YFAS 2.0 [12], that has already been translated into German [13], and used in other studies [14].

The new version evaluates 11 symptoms of FA following the DSM-5 criteria of SRAD: overeating (Criterion 1), desire to cut down (Criterion 2), time spent (Criterion 3), craving (Criterion 4), related impairment (work/school, family, social relationship) (Criterions 5–7), risky use (physically hazardous, detrimental physical/psychological consequences) (Criterions 8–9), tolerance (Criterion 10), and withdrawal (Criterion 11).

Given the increasing interest on this topic, it is important that researchers and clinicians can benefit of having a reliable tool to evaluate FA at their disposal.

Currently, only the first version of YFAS is available in Italian [15], and to the best of the authors’ knowledge, no validation of the YFAS 2.0 has been conducted with an Italian sample. Therefore, with this study, we aimed at translating YFAS 2.0 into Italian and to assess the psychometric properties of this instrument on a non-clinical sample of Italian university students.

Materials and methods

Participants and procedure

Data collection was conducted from October to December 2016. Students in their first and third years of the School of Medicine from the University “Magna Graecia” of Catanzaro (Italy) were given the opportunity to participate in this research. The aim and the description of the research were posted on the Facebook page of the Ambulatory for Clinical Research and Treatment of Eating Disorders of Catanzaro (Italy). The online survey included a contextual informed consent, a self-report form to collect socio-demographic variables, and the questionnaires. Data were collected anonymously.

A total of 574 participants (57% women, n = 327) completed all questions. Participants’ height and weight were obtained by self-report. Mean age was 21.42 ± 2.3 and no differences were evident between genders (male = 21.62 ± 2.7; female = 21.66 ± 2.0; t = −1.817; p = 0.70).

Mean body mass index (BMI) was 22.5 ± 3.9 kg/m2, and, as expected, males presented higher BMI than females (male = 23.86 ± 3.9; female = 21.4 ± 3.6; t = −7.821; p < 0.001). Most participants were normal weight (73.7%; n = 423; BMI = 18.50–24.99 kg/m2) and few were underweight (7.8%; n = 45; BMI < 18.50 kg/m2), overweight (15.2%; n = 87; BMI = 25.00–29.99 kg/m2), or obese (3.3%; n = 19; BMI ≥ 30.00 kg/m2).

Measures

Yale Food Addiction Scale 2.0 (YFAS 2.0)

The Italian translation of the YFAS 2.0 was carried out through a double forward- and back-translation procedure. The authors independently translated the English version of the scale into Italian. After a consensus among translators was achieved, an Italian–English researcher blind to the original version translated this preliminary version back into English. The newly developed Italian version of the YFAS 2.0 was administered to 25 participants (not included in the present study) to check the comprehension of the items before being used in this study. All 25 found it comprehensible and easy to provide ratings.

The YFAS 2.0 assesses addiction-like eating behavior during the past 12 months. The scale consists of 35 items, which are scored on an eight-point scale ranging from never (score = 0) to every day (score = 7) that account for 11 symptoms. Note that there is no sum score calculated from the single items of the YFAS 2.0; each of the 11 diagnostic criteria was considered fulfilled if one or more of the relevant questions for each criterion reached the threshold (Appendix 1 in Electronic supplementary material). A final symptom count score can be calculated by adding up all endorsed symptoms; thus, scores can range from 0 to 11. Another score regards the severity level that is described according to the diagnostic thresholds for SRAD in DSM-5: mild FA (when 2–3 symptoms are present), moderate FA (when 4–5 symptoms have been recognized), and severe FA (when ≥6 symptoms are present). Finally, every FA diagnosis also requires the presence of the impairment or distress criteria.

Beck depression inventory

Depressive symptoms were measured using the Beck Depression Inventory (BDI) [16], which consists of 21 multiple-choice items, rated from 0 to 3. Scores between 0–9, 10–16, 17–29, and ≥30, respectively, indicate minimum, mild, moderate, and severe depression. Participants with total BDI score >16 were considered as clinically depressed in the present study [17]. Cronbach’s alpha in the present research was 0.79.

Binge eating scale

We used the Binge Eating Scale (BES) to measure binge eating severity [18]. This test is made up of 16 items describing the behavioral manifestations, feelings, and cognitions associated with binge eating. A total BES score <17 indicates unlikely binge eating disorder (BED), a score between 17–27 indicates possible BED, and values >27 indicate probable BED. The internal consistency in this study was 0.90.

Eating disorder examination-questionnaire

The Eating Disorder Examination-Questionnaire (EDE-Q) is a 28-item instrument for the assessment of eating disorder symptoms within the past 28 days [19]. Twenty-two items can be reduced to four subscales: eating restraint, eating concern, weight concern, and shape concern. The remaining six questions assess the frequency of eating disordered behaviors. Internal consistencies of the subscales ranged between α = 0.91–0.95 in the current study.

Pittsburgh sleep quality index

The Pittsburgh Sleep Quality Index (PSQI) measures sleep quality, latency, duration, efficiency, disturbances, daytime dysfunction, and sleep medication use [20]. A global score, obtained by adding the subscales, is used to classify good versus bad sleepers. The internal consistency in this study was 0.66.

The Italian validated versions of the tests were used in the present study.

Data analyses

A confirmatory factor analysis (CFA) for dichotomous data was conducted using M-plus [21] to examine whether the 11 YFAS 2.0 symptoms had an underlying one-factorial structure. Therefore, factor structure and internal consistency of the YFAS 2.0 are calculated at the symptoms and not at the items level [12, 13]. Items assessing impairment or distress were not included in this analysis as they reflect clinical significance of the full syndrome rather than being indicators of individual criteria [12, 13]. The comparative fit index (CFI), Tucker–Lewis index (TLI), weighted-root-mean-square residual (WRMR), and the root-mean-square error of approximation (RMSEA) were used to evaluate the model. Internal consistency of the 11 YFAS 2.0 symptoms was evaluated with Kuder–Richardson’s alpha for dichotomous variables.

Construct validity was determined by partial correlations with the respective questionnaires controlling for gender. Finally, following the procedure of Gearhardt et al. [12], the scores of participants to these questionnaires were compared according to the severity levels of YFAS 2.0. A p < 0.05 was considered statistically significant.

Results

Prevalence of FA in the sample

Twenty participants (3.4%) from the sample resulted positive for at least two symptoms of the scale with clinically significant/impairment or distress. FA was more frequent among female participants (female = 5.5% vs male = 0.8%; χ 2 = 9.223; df = 1; p = 0.002). According to severity 3 (0.5), 5 (0.9) and 12 (2.1%) respectively received a mild, moderate, and severe YFAS 2.0 diagnosis.

Women (0.69 ± 1.81) had a higher mean criteria total score than men (0.28 ± 0.96) (t (572) = 3.243; p < 0.001), and even if this effect was small (η 2 = 0.018), successive correlations were performed after controlling for gender.

Symptoms’ factor structure and reliability

We used a mean- and variance-adjusted weighted least square (WLSMV) estimator which is indicated for categorical data.

The CFI (0.958), the TLI (0.974), the WRMR (0.794), the RMSEA (0.031), the 90% confidence interval of RMSEA (0.015–0.045), and probability RMSEA (0.991) suggested good fit for the one-factor model. Besides, we observed: χ 2 = 68.145, df = 44, and p = 0.0113.

All criteria had factor loadings for the single factor of 0.79 or higher (Table 1), and Kuder–Richardson α = 0.87 suggested good internal consistency reliability.

Table 1 Frequencies, factor loadings, kurtosis, and skewness of the Yale Food Addiction Scale 2.0 criteria
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Table 1 shows the frequencies of participants who met FA criteria as well as the Skewness and Kurtosis indexes. These indicated that the distribution was not normal.

Convergent validity

As displayed in Table 2, the YFAS 2.0 symptom count scores were significantly correlated with other measures (ranging from 0.17 to 0.69).

Table 2 Spearman’s correlations between YFAS 2.0 symptom count and convergent and divergent measures
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Anova results show that the severity level of YFAS 2.0 (Table 3) successfully discriminated the severity of eating-related constructs, binge eating, depressive symptoms, and sleep quality index (all p < 0.001).

Table 3 Comparison of questionnaires according to YFAS 2.0 severity
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Discussion

The present study aimed at validating the Italian version of the YFAS 2.0 in a large non-clinical sample. FA has catalyzed the interest of researchers in relation to a wide number of clinical conditions in the last years [22,23,24,25,26,27,28] and the number of validations in different languages of the previous version further supports the importance of this pathological behavior.

The current study indicates that the Italian version of YFAS 2.0 is a solid tool with good psychometric properties and robust reliability and a fully comparable structure to the original version of one-factorial structure. Moreover, severe YFAS 2.0 diagnoses were more common than those with mild or moderate severity, and this is consistent with the English [12] and German [13] versions.

The relationship between FA and age is somehow controversial [29, 30]. We observed no association between YFAS 2.0 and age, but, importantly, our research was done on a sample of young students. Recently, Schulte and Gearhardt [31] found that younger individuals reported elevated addictive-like eating behaviors and that the relationship, although small, was significant for the YFAS 2.0. Instead, more women resulted positive to the screening; this is in line with two studies where a higher prevalence of FA was found in women than in men [9, 32]. Other authors have not found any association between gender and YFAS 2.0 scores [31].

Our data demonstrated a positive correlation between YAS 2.0 and BMI. Recent studies [31, 33,34,35,36] have confirmed the higher prevalence of FA among obese participants with the previous version of this test.

Regarding convergent validity, the YFAS 2.0 was highly correlated with EDE-Q subscales and total score, reflecting a positive correlation between FA and eating psychopathology. Accordingly, we do replicate the German validation of YFAS 2.0 [13], with the only exception of the “restraint” dimension. In fact, a small, positive correlation with the restraint subscale of EDE-Q was observed, and this is consistent with the assumption that food addiction can be present among patients with anorexia nervosa (AN) [37]. In fact, not rarely, patients with AN fear not being able to stop eating when they taste a food that they like very much. In other cases, even if AN patients avoid any food that could make them gain weight, they cannot help stop eating a small quantity of some “dangerous food” (e.g., chocolate, sweet drinks, bread, …) to which they are “addicted”. In fact, the restrictive behavior driven by AN patients could be interpreted as an effort to fight against an internal subjective impulse for food or hedonic eating [8, 38].

Besides, in our research, we found a high positive correlation between YFAS 2.0 and BES scores. Schulte and Gearhardt [31] obtained a high correlation between food addiction and binge frequency. Curtis and Davis [39] found that both BED and not-BED obese subjects endorse a great number of the DSM-5 criteria for FA, although BED subjects appeared to be more severely addicted, since they endorsed more symptoms than their non-binging counterparts. A study has shown that BED and FA are related but not identical as only 57% of obese adults who had binge eating met the diagnosis of FA [40]. Another investigation [41] has demonstrated that, despite a highly significant relationship between BED and FA, the YFAS covers much more the physical symptoms of withdrawal, while BES focuses on the cognitive aspects and feelings associated with the episode of binge; thus, FA cannot replace binge eating assessment.

We also found a positive correlation between total YFAS 2.0 and PSQI scores. Nolan and Geliebter, studying the relationship between FA and night eating syndrome also found a similar result [42]. In the same way, the high correlation between YFAS 2.0 and BDI is consistent with previous studies, proving that the diagnosis of FA was associated with greater depressive symptomatology [43,44,45].

Although this study has demonstrated the good psychometric properties of the Italian YFAS 2.0 version, there are few limitations that authors want to address.

First, in the present study, all information was obtained via self-report, which could be potentially biased (e.g., height and weight); and second, it was an Internet-based data collection that could result in a selection or response bias [46]. Yet, online surveys have demonstrated to produce comparable results to those obtained from paper-and-pencil versions and that psychometric properties of questionnaires do not benefit or prejudice from the different methods [46, 47].

Third, our sample predominantly consisted of young, normal weight medical students, so it could be argued that results should be circumscribed and comparable to similar populations. Several explanations can be given to justify this choice. Most addictions (substance or behavioral addictions) have the onset in young age, and this was the main reason to drive our choice towards young participants. On the other hand, the validation of a test in a foreign language has the goal to demonstrate that the new version matches with the original one, whose validity has been already demonstrated by the authors who created the test. In our case, the results have demonstrated that the Italian validation of the YFAS 2.0 widely overlaps with those of the original version [12] in this large sample of medical students. Nevertheless, authors consider that future studies with a clinical sample of Italian patients could replicate and extend the present findings.

Conclusions

In conclusion, the psychometric properties of the Italian version of YFAS 2.0 are largely equivalent to the original version with a high internal consistency. Thus, the Italian version of the YFAS 2.0 has demonstrated in a sample of university students to be a useful tool to investigate food addiction.