Here is the design of a clinical trial:

Official Title: Treating Nightmares in Posttraumatic Stress Disorder with Dronabinol: a Randomized Controlled Study (THC PTSD-trial)

Included conditions:
- Posttraumatic Stress Disorder

Study Armgroups:
- {'label': 'BX-1 (dronabinol)', 'type': 'EXPERIMENTAL', 'description': 'BX-1', 'interventionNames': ['Drug: BX-1']}
- {'label': 'Placebo', 'type': 'PLACEBO_COMPARATOR', 'description': 'Placebo of BX-1', 'interventionNames': ['Drug: Placebo']}

Interventions:
- {'type': 'DRUG', 'name': 'BX-1', 'description': 'BX-1 (dronabinol), oral solution. All patients enrolled establish their individually tolerable dose by dose Titration.', 'armGroupLabels': ['BX-1 (dronabinol)']}
- {'type': 'DRUG', 'name': 'Placebo', 'description': 'Placebo of BX-1, oral solution', 'armGroupLabels': ['Placebo']}

Primary Outcomes:
- {'measure': 'Frequency and intensity of nightmares', 'description': 'Frequency and intensity of nightmares, measured with the Clinician-Administered PTSD Scale-IV (CAPS-IV) B2 score for the last week, range 0-8. A lower score indicates less frequent and/or intense nightmares.', 'timeFrame': '10 weeks'}

Please estimate the sample size based on the assumption: 
The sample size calculation is based on a two-sided, two-sample t-test with a power of 0.8. An adjustment for baseline scores in an ANCOVA model is applied. A 10% dropout rate is assumed.
Sample size
        The sample size calculation is based on the primary endpoint âClinician-Administered PTSD Scale-IV (CAPS-IV) B2 score at 10Â weeksâ in the full analysis set including all randomized patients who received the study medication at least once. The aim is to show a lower average score at 10Â weeks in the intervention group (I) than in the control group (C). Sample size calculation will be based on a two-sided, two-sample t-test. Adjustment for baseline scores in an ANCOVA model which is applied for the primary efficacy analysis will increase the power compared with a two-sample t-test, which ignores the influence of different baseline values. Therefore, this strategy for sample size calculation is a conservative procedure. In a random-effects meta-analysis of four RCTs investigating the effect of prazosin on PTSD nightmares, a combined standardized mean difference (Cohenâs d) of 0.5 (95% CIâ=â0.03â0.96) was observed [1]. We conservatively assume a standardized effect which is a little smaller and given by 0.45. This assumed effect can be considered as clinically relevant because distressing nightmares are an independent risk factor for comorbidity and severity in PTSD patients. Nightmares also contribute to alcohol and substance abuse, suicidal ideation, and even completed suicide [17]. As studies assessing minimal clinically important difference (MCID) for reduction of nightmares in PTSD are currently missing, clinical significance cannot be used to calculate sample size.
        The required sample size to detect this effect of 0.45 with a power of 0.8 is 158 (79 per group) calculated with nQuery Version 8.2.1.0. We conservatively assume that there will be no more than 10% of patients who are randomized but never get the study medication. Therefore, the total number of patients to be recruited is 176 (158/176â=â0.9) or 88 per group.