Although a sizable percentage of the present sample reported frequent and/or distressing nightmares, none of the adolescents had ever sought professional help for their problem. This value is even lower compared to the findings in adults [17, 25, 28, 36]. Most of the participants knew about a possible treatment strategy (almost 90%), a percentage much higher compared to the two thirds of participants with clinically significant nightmares who believed nightmares cannot be treated [17].

Whereas 15 to 30% of adults with frequent nightmares have sought professional help [17, 25, 28, 29, 36], none of the adolescents had done so. Interestingly, adolescents rarely seek help for mental health problems of any kind—only if the parents actively motivated the adolescent [15, 18]. In case of nightmares, this is a problem, as parents quite often tend to underestimate their children’s nightmare frequency [26], possibly because older children do not tell every nightmare their parents. On the other hand, research in adolescents indicates that nightmares can be associated with depression [37, 38], suicidal thoughts [5], and self-injury [14]. These associations have also been reported for adults [13, 27] and can be a hint toward trauma exposure [33]. Based on this, the question of how diagnosis and treatment of possible nightmare disorders in adolescents could be improved is of utmost importance.

The gender difference regarding nightmare frequency, with females reporting more frequent nightmares compared to males (see regression analyses), is in line with a meta-analysis regarding gender differences in nightmare frequency [31], as especially in adolescents and young adults, the effect sizes were most pronounced. Interestingly, in adults, it was also found that gender contributes to nightmare distress even though nightmare frequency was statistically controlled for [27]. It seems that females are more prone to the negative effects of frequent nightmares than males.

From a methodological viewpoint, it has to be considered that the sample is relatively small and possibly not representative for the German population of adolescents. The school type Gymnasium designates higher education compared to the two other types of high school, i.e., Hauptschule and Realschule. In 2018, about one third of German school attendees completed the highest education (Hochschulreife), whereas about 40% completed the mittlere Reife and about 20% the Hauptschulabschluss [34]. This indicates that the sample is biased towards high education levels. In contrast to studies in adults, especially in students, this sample included an equal number of girls and boys; this is in line with previous dream studies carried out in schools [24, 30] and reflects the gender distribution in schools. The gender distribution in student samples, especially among psychology students, is more shifted toward a higher percentage of females (see, for example, [32]). Similarly, in dream studies carried out online, females outweigh males, as women are more interested in dreams and, therefore, more likely to participate in dream studies (see, for example, [22]). Thus, the balanced ratio of girls and boys in the present sample indicates that selection bias regarding gender was minimal.

However, the nightmare questions were embedded in a more general dream questionnaire; thus, it seems unlikely that the sample was biased in the direction of nightmare sufferers. Nightmare frequency was elicited retrospectively; as research [19] has indicated that prospective measures yielded higher nightmare frequency means compared to retrospective measures, there might be a possible underestimation of nightmare sufferers in the present sample. However, the difference between the two types of nightmare frequency measures is relatively small (effect size d = 0.101) [40]. Thus, a possible underestimation of nightmare sufferers is likely to be small and, if present, would show even more clearly the problem of a respective lack of help seeking in this population.

Overall, the present study clearly indicates that there is a gap between adolescents suffering from nightmares and the percentage of adolescents treated for their nightmare condition. In the current study, the students received leaflets explaining the basic principles of imagery rehearsal therapy [11] for display when they present their findings to the school audience. The high percentage of adolescents knowing about lucid dream therapy might be due to popular media, e.g., the movie “Inception [7]”; thus, media and social media might be important outlets in order to inform this age group about possible nightmare treatment options. In addition, it also seems important to educate parents to ask their children about nightmares and support them in case treatment is needed. If successful, this would reduce the percentage of adult nightmare sufferers considerably.