**1.2. Nightmares in PTSD**

It is estimated that 19–71% of trauma victims diagnosed with PTSD have frequent nightmares, compared to only 2–5% of the general population [6]. These percentage ranges are due to lack of consensus on the definition of a nightmare. The *DSM-5* defines nightmares as "repeated occurrences of extended, extremely dysphoric, and well-remembered dreams that usually involve efforts to avoid threats to survival, security, or physical integrity…" and can only be diagnosed as such if the nightmares do not occur exclusively during the course of another mental disorder. In the *International Classification of Sleep Disorders* (*ICSD-2*) [7], the definition is more inclusive, calling upon "recurrent episodes of awakenings from sleep with recall of intensely disturbing dream mentations1 , usually involving fear or anxiety, but also anger, sadness, disgust, and other dysphoric emotions." Some experts in the field also propose their own definition, as illustrated by Zadra and Donderi [8], who describe nightmares as "very disturbing dreams that awaken the sleeper."

The presence of nightmares seems to be related to the prevalence and severity of PTSD [9]. A recent prospective longitudinal cohort study in combat Veterans indicated that the report of pre-deployment nightmares was associated with an increased risk for the development of

<sup>1</sup> Mental activity.

PTSD symptoms [10]. Furthermore, one review reported that of victims experiencing nightmares within 1 month of the trauma, 33% went on to develop PTSD, whereas 9% did not [11]. As a result, nightmares may contribute to PTSD symptom maintenance.

(DSM-5), it is first necessary to have been exposed to a traumatic event, and, as a result of that exposure, to experience symptoms from each of the following four symptom clusters: intrusion (e.g., disturbing recurring flashbacks or dreams); avoidance of memories of the event; negative alterations in cognitions and mood; and alterations in arousal and reactivity (e.g.,

To date, the recommended treatment by the International Society for Traumatic Stress Studies is trauma-focused cognitive behavioral therapy (CBT) [2]. This treatment involves several strategies, including: psycho-education on PTSD reactions; training in relaxation strategies to counteract anxiety; cognitive restructuring by challenging, for example, maladaptive traumarelated appraisals; and exposure. Exposure requires the victim to confront his or her fears, which can be done in two ways: (1) through repeated exposure to the trauma memory, either in imagination or through the writing of a narrative; and (2) in vivo exposure to situations associated with the trauma. The rationale is to help change the victim's perception of a situa-

The efficacy of trauma-focused CBT is widely documented compared to other types of psychological treatments, such as psychodynamic psychotherapies, or supportive techniques (e.g., [3]). However, in a multidimensional meta-analysis by Bradley et al. [4], including 26 studies and 44 treatment conditions, the authors raised the question on the type of exclusion criteria used in these studies when looking at their efficacy, such as comorbid disorders. Then, in a review by Bisson and Andrew [5], their findings remind that the high numbers of dropout remained an issue. Considering these results, we may say there is still room for improve-

It is estimated that 19–71% of trauma victims diagnosed with PTSD have frequent nightmares, compared to only 2–5% of the general population [6]. These percentage ranges are due to lack of consensus on the definition of a nightmare. The *DSM-5* defines nightmares as "repeated occurrences of extended, extremely dysphoric, and well-remembered dreams that usually involve efforts to avoid threats to survival, security, or physical integrity…" and can only be diagnosed as such if the nightmares do not occur exclusively during the course of another mental disorder. In the *International Classification of Sleep Disorders* (*ICSD-2*) [7], the definition is more inclusive, calling upon "recurrent episodes of awakenings from sleep with

anger, sadness, disgust, and other dysphoric emotions." Some experts in the field also propose their own definition, as illustrated by Zadra and Donderi [8], who describe nightmares

The presence of nightmares seems to be related to the prevalence and severity of PTSD [9]. A recent prospective longitudinal cohort study in combat Veterans indicated that the report of pre-deployment nightmares was associated with an increased risk for the development of

, usually involving fear or anxiety, but also

tion and his or her reaction to this specific and problematic situation.

irritability and sleep disturbance).

78 Cognitive Behavioral Therapy and Clinical Applications

ment of trauma-focused CBT.

recall of intensely disturbing dream mentations1

as "very disturbing dreams that awaken the sleeper."

**1.2. Nightmares in PTSD**

1

Mental activity.

Also, the treatment of nightmares is complex because of the varying conceptualization of nightmares. On one hand, they represent one of the symptoms of the PTSD intrusion cluster and are conceptualized as a normal reaction following a traumatic event [12]. As a result, it is commonly believed that CBT for PTSD will be sufficient to effectively treat them (e.g., [3]). On the other hand, nightmares have an independent diagnosis in the *DSM-5* [1] and in the second edition of the *International Classification of Sleep Disorders* (*ICSD-2*) [7].

Furthermore, different fields of study (i.e., sleep and dream field vs. PTSD field) conceptualize post-traumatic nightmares (PTNM) differently. In the PTSD field, several models have been developed to explain PTSD emergence, and PTNM are considered an intrusive symptom of this disorder. For example, in the Foa and colleagues model, the authors argued that an entire memory network is created at the time of the trauma. PTNM could be one element of this network, which is reactivated during sleep by ongoing hyperarousal. However, in the dreaming field, PTNM are related to different dream theories and authors reflect on the purpose and function of dreams. For example, Hartmann advances that dreaming is an adaptive function to emotionally adjust to trauma.

Finally, authors also diverge on whether PTNM are a comorbid disorder, rather than a symptom of PTSD [13]. Some authors conceptualize PTNM in two steps after a traumatic event: immediately following a traumatic event, PTNM are considered a trauma-induced symptom of PTSD (B criterion), whereas later, PTNM are perceived as learned behavior and, therefore, would become distinct from PTSD symptoms. According to Krakow and Zadra [14], nightmares persist because the victim is not able to process information related to the event and to the nightmare. The person fears and, therefore, avoids them. As a result, the recollection of the trauma is not incorporated in memory. In addition, as the victim begins to fear going to bed and develops poor sleep hygiene (e.g., drinking alcohol before going to bed or napping during the day), or as nightmares interrupt sleep, sleep becomes fragmented, potentially leading to sleep loss, and ultimately insomnia [12].

Considering nightmares in two steps (i.e., first as a PTSD symptom, then as a learned behavior and comorbidity) offers the opportunity to treat them differently. In fact, the first step represents the traditional view, and nightmares can be treated with conventional CBT for PTSD, while the second step allows targeted treatment for nightmares as a comorbidity.
