**Core Concept**
Post-traumatic stress disorder (PTSD) is a psychiatric condition triggered by a traumatic event, characterized by symptoms such as flashbacks, nightmares, and avoidance of triggers. The onset of PTSD can occur immediately after the traumatic event or months later, with the exact timing varying among individuals.

**Why the Correct Answer is Right**
Individual debriefing and early counseling have been widely studied, but research has shown that they are not the most effective methods of treatment for PTSD. In fact, a 2007 Cochrane review found that early psychological interventions, including debriefing, do not prevent the development of PTSD in individuals who have experienced trauma. This is because PTSD is a complex disorder that requires a comprehensive treatment approach, often involving medication and prolonged therapy.

**Why Each Wrong Option is Incorrect**
**Option A:** The onset of PTSD may indeed occur many months after the traumatic event, which is a characteristic feature of the condition. This is because the body's response to trauma can be delayed, and the individual may not fully process the event until later.

**Option C:** Eye movement desensitization and reprocessing (EMDR) is a form of therapy that has been shown to be effective in treating PTSD. EMDR involves the use of eye movements or other forms of bilateral stimulation to process traumatic memories and reduce symptoms.

**Option D:** There is a high risk of substance abuse, including alcohol, in individuals with PTSD. Studies have consistently shown that individuals with PTSD are at increased risk of developing substance use disorders, which can exacerbate symptoms of PTSD.

**Clinical Pearl / High-Yield Fact**
A key aspect of treating PTSD is the use of trauma-focused cognitive-behavioral therapy (TF-CBT), which has been shown to be effective in reducing symptoms of PTSD. TF-CBT involves the use of cognitive restructuring, exposure, and other techniques to help individuals process traumatic memories and develop coping skills.

**✓ Correct Answer: B. Individual debriefing and early counselling are most effective method of treatment**