We administered the Social Phobia and Anxiety Inventory (SPAI; Turner, Beidel, Dancu, & Stanley, 1989) to 2,505 students in the third and fourth year of Compulsory Secondary Education (Enseñanza Secundaria Obligatoria, ESO) and first year of High School (Bachillerato) in seven randomly selected public and state-subsidized high schools from the Spanish region of Murcia.

In the second stage of the study, we selected participants based on a previously determined cut-off point cutoff-point (SPAI-SP ≥97; Olivares, García-López, Turner, La Greca, & Beidel, 2002). Participants in this subset were assessed with the Anxiety Disorders Interview Schedule for DSM-IV (ADIS-IV-C; Silverman & Albano, 1996): 132 met the criteria for the diagnosis of generalized social phobia (GSP). They and their parents were informed of the assessment results. Inclusion criterion: meet the requirements for GSP diagnosis (American Psychiatric Association (APA), 2000); 108 met the criteria (M=15.4 years; SD=1.11; range: 14–17; 63% were female). Exclusion criteria: not presenting written consent signed by at least one parent or equivalent, meeting the diagnostic criteria for severe psychopathology (e.g., depression or narcissistic disorder), long history of substance abuse, aggressive behavior, missing three consecutive treatment sessions, and not having previously received psychological or psychiatric treatment.

Evaluation of participants’ expectations (outcome expectancy, OE). At pretest, we used an ad hoc one-item scale (range: 0–5) in which participants indicated the extent to which they hoped to improve from treatment (0=Not at all; 5=A lot). All participants completed the following measures at pretest, post-test, and follow-up.

The Social Phobia and Anxiety Inventory (SPAI; Turner et al., 1989). In this application, the SPAI-SP subscale showed an internal consistency of .89 (Cronbach's alpha).

Anxiety Disorders Interview Schedule for DSM-IV. Child Version (ADIS-IV-C; Silverman & Albano, 1996). In this application with a Spanish adolescent population, the value of k oscillated between .83 and .91.

The number of social situations feared and/or avoided (NSSFA) was quantified based on the information initially provided by participants in the SP section of ADIS-IV-C; these data were used to calculate the clinical significance of the treatment effect.

Personal Report of Confidence as a Speaker (PRCS; Gilkinson, 1942). In this application, the value of α was .89.

Rosenberg Self-Esteem Scale (RSE; Rosenberg, 1965). In our investigation, its internal consistency was .90 (Cronbach's α).

The Rathus Assertiveness Schedule (RAS; Rathus, 1973). In this application, Cronbach's alpha internal consistency was .78.

Duration of eye contact (DEC) with the examiner is quantified through its registration in an observation test and was also performed at pretest, post-test, and follow-up. It included three interviews with each participant, who had to initiate and maintain a conversation with a stranger for 3min. The topics were participants’ expectations about the psychological treatment (pretest), their personal assessment of the treatment received and suggestions for improvement (post-test), a description/assessment of the difficulties they had faced and how they had solved them (follow-up). This test was led by two examiners of different genders, with more than two years of experience in the treatment of individuals with SAD. Each interacted with participants of the opposite sex and were trained not to initiate or carry the weight of the conversation with the participants not to initiate the conversation but they should confront/solve the difficulties might arise.

After obtaining the written consent of participants and their parents, each participant's performance was filmed with a video camera to record the total DEC with the examiner. The recordings were viewed and coded by two independent observers previously trained for the purpose. Interobserver correlations were high: k=.91.

Adherence to treatment (ATT). This variable was quantified as a function of the “homework” performed and the “number of training sessions” attended.

This research was granted permission by the Ethical Research Committee of the University of Murcia. Fourteen trained examiners performed the assessment. They were grouped in opposite-sex pairs of individuals who are graduates in psychology and were trained to independently carry out their tasks. Two participated in the pretreatment evaluation, two in the screening (pretest), six in the clinical interview, two performed the post-treatment evaluation, and two others the follow-up. All were blinded to treatment, and the reliability coefficient for GSP diagnosis was good (k=.86).

The selected adolescents and their parents were sent a letter that presented the objectives, structure, content, and other issues related to the intervention. They were also advised that they could clarify any doubts by requesting a private meeting or by telephone conversation with an expert on the toll-free number provided to them.

The 108 participants with GSP were randomly assigned to one of three experimental conditions: Waiting-list control group (WLCG 64% girls) or one of two treatment groups the intervention in adolescents with social phobia (IAFS 62% girls) and IAFS without the SST (IAFS-R 65% girls), with 36 participants in each group.

We chose a two-factor partially repeated measures experimental design. The repeated measures factor contained data recorded at different times, and the between-subject factor was the IAFS, which was divided into two categories (IAFS and IAFS-R). For ethical reasons, after the post-test, participants in the WLCG and the dropouts were offered the possibility of joining a non-experimental treatment group.

The treatment was applied by two psychology graduates, of different genders and with more than ten years of experience treating groups of adolescents with GSP; the roles of therapist and co-therapist were randomly assigned. Treatment integrity was controlled using two identical manuals (see Olivares, 2005), except in the section on SST (IAFS and IAFS-R). Therapists’ knowledge of the program was controlled by two interviews conducted independently by two observer interviewers, who followed a structured interview previously prepared by two psychologists with broad experience in applying the IAFS Program. The items covered the most relevant aspects of the programs’ content, structure, and development. The IAFS consists of 12 weekly 90-min group treatment sessions. The program's basic components are as follows:

Educational component. Information about the contents of the treatment is provided, presenting an explanatory model of SP, planning the desired achievements—target behaviors—and reviewing the individual's expectations for the treatment.

SST. This includes contents/activities such as starting and maintaining conversations, assertiveness, paying and accepting compliments, making and keeping friends, and training in public speaking.

Exposure. This is the core of the program, and most activities revolve around it. Both in vivo—simulated and real—and imaginary types of exposure are used.

Cognitive restructuring techniques. This component is aimed at teaching the participants to identify the negative automatic thoughts they generate when they evoke past situations, anticipate social situations, or are immersed in a social situation that triggers anxiety responses.

At the end of the group sessions, homework assignments are given. The sessions are devoted to monitoring the difficulties encountered in the homework assignments and dealing with issues related to the content and activities of the group sessions. The IAFS-R is a written version of the IAFS manual, built ad hoc, in which all its content is structured identical to full version (IAFS) except in the section dedicated to the SST. To control for reactivity by frustration, the groups were treated in different places, to prevent them from being aware of the existence of the other; both places were two classrooms in public teaching centers with identical layout and furniture, furthermore the treatment was applied in the same time slot.

Participants had two hours a week, on two separate, predetermined days, for individual telephone consultations during which they could request information about the homework and resolve doubts about the contents given during the treatment sessions.

Statistical analyses were performed with the SPSS 19.0 program. The magnitude of the effect size (ES) was interpreted following Cohen (1988). Positive values of d indicate better results from the group that comes first in the comparison. As the experimental mortality exceeded 10% in one of the groups, the loss of participants was controlled by imputation of lost data; the outcome data of these dropouts were included in intent-to-treat analyses using multiple imputation. Thus, data analysis was based on all patients who were assigned to one of the three study arms. The clinical significance of the results was calculated from the reduction/elimination and increase of the NSSFA. To control inflation of the type I error rate, the Bonferroni correction procedure was applied so that, to maintain the nominal significance level at 5%, the critical probability level associated with the contrast statistic result had to be equal to or less than 0.017 (αB=α/3=0.05/3=0.017).

The study of the equivalence of the groups in the pretest did not show statistically significant differences in the variables: age, sex distribution, family history of SP, alcohol consumption, or cannabis-related disorders. Similarly, no statistically significant differences were found with the dependent variables, contemplating and without contemplating the abandonments, except in the variables RSE (p=.016) and RAS (p=.021), whose averages in the IAFS were higher than in the IAFS-R. There were also no significant differences between the treatment groups for OE, in the pretest, and only when the data of those who completed the treatment were analyzed.

The percentage of dropouts in the IAFS-R was 33.3% (12 participants), 5.6% (2 participants) in the IAFS group, and 0% in the WLCG. The differences were statistically significant between the three groups [RV (2)=20.03, p<.0001] and between IAFS and IAFS-R [2 (1)=8.86, p=.003].

To study their equivalence, both groups (14 vs. 58) were compared. There were no significant differences in age [t (70)=−0.92, p=.358] or in sex [2 (1)=1.91, p=.166], although the number of women was greater (78.6% vs. 58.6%). There were no significant differences in family history of SP (RV (1)=0.70, p=.402), alcohol consumption (RV (1)=0.07, p=.781) and cannabis consumption=0.04, p=.840). In the last three analyses, we applied the likelihood ratio test because the conditions required for the chi-square test had not been met.

There were also no significant differences in the dependent variables and in comorbidity, except in OE in favor of the completers and in the panic attacks that were more frequent in the dropouts (64.3% vs. 25.9%). Those who dropped out reported higher NSSFA and scored more in SPAI-SP, RAS. This trend was also found in dysthymic disorder (85.7% vs. 74.1%).

The IAFS obtained magnitudes higher than the IAFS-R with statistically significant differences in the two measured variables (see Table 1). The effect size (ES) was medium and high.

Treatment groups showed improvements from pretest to post-test in all variables analyzed; in WLCG only the variable RAS showed an improvement. To examine in which groups the differences occurred, post hoc comparisons were made (Table 2).

The groups receiving treatment showed highly significant changes in their favor, with large ES. The WLCG did not show any. The IAFS vs. IAFS-R was favorable to the first one of five variables, but not in PRCS, despite the fact that ES was favorable and significant, Cohens's d=0.20, and not in PRCS because ES was superior in IAFS-R. The study of pretest follow-up changes at 6 months (Table 2) also shows significant differences in favor of IAFS in five of the seven variables, with ES being relevant and favorable to it. Analysis of the pretest follow-up changes at 12 months shows that both groups presented improvements, but the changes in IAFS were superior and with significant differences in their favor, except in PRCS. All ESs were above 0.50 except in PRCS (Table 2).

We assessed participants based on the reduction/elimination of the number of feared and/or avoided social situations they reported at pretest (ADIS-IV-C) using three criteria: (a) recovery (100% remission—the criteria required by the DSM-IV for the diagnosis of GSP are no longer met); (b) improvement/remission between 99.99% and 0% of NSSFA; and (c) increase/aggravation in NSSFA. To verify possible differences, we applied the chi-square test to each contingency table. Assessment of the equivalence of the groups at pretest did not show statistically significant differences between experimental conditions.

In the study of clinical significance of changes (Table 3) in the pretest–post-test, statistically significant differences were observed between the three experimental conditions. Analysis showed that these were significant in: (a) IAFS vs. IAFS-R [2 (3)=19.31, p<.001) because the percentage of participants with a reduction of less than 50% of NSSFA in IAFS-R was 52.8% compared to 8.3% in IAFS; (b) IAFS vs. WLCG [2 (4)=61.89, p<001] and IAFS-R vs. WLCG [2 (4)=37.26, p<.001] because in both cases the reduction of NSSFA was greater in the treatment groups.

In the pretest-follow-up comparison at 6 months, significant differences were found between IAFS and IAFS-R, with the first presenting a higher percentage of recoveries and improvements (between 75% and 99.99%). In the study at 12 months, the differences between IAFS and IAFS-R were also significant because the first one presented recoveries greater than the second, with superiority in improvements between 75% and 99.99%, but not lower than 75%.