Final answer:
The most likely cause for the behavior described is marijuana abuse, due to the symptoms of forgetfulness, impaired coordination, and unusual financial decisions, which align with substance abuse effects. A new neighbor moving in may suggest a potential source of the substance, but healthcare providers should conduct a full assessment to rule out other physical or mental health issues.
Step-by-step explanation:
The most likely cause for the son's behavior, which includes forgetfulness, falls, and unusual spending is D. Marijuana abuse. The symptoms presented by the teenager, such as memory lapses, impaired motor coordination (falling down stairs), and unusual behavior (making an expensive purchase from an infomercial), are consistent with substance abuse, particularly of marijuana. A new neighbor moving in around the time the symptoms started could potentially indicate a new source of the substance. These behaviors are not typically representative of peer conflict, average adolescent behavior, or simply sleep loss in isolation, especially if they show a marked and sudden change from previous behavior.
It is essential to consider physical and mental health conditions that might manifest similarly, such as concussions or mental health disorders like depression or bipolar disorder, which can affect memory, judgment, and behavior. However, given the available information, marijuana abuse is the most likely cause. It's crucial for healthcare providers to further evaluate the teenager's condition through a comprehensive assessment that may include a physical examination, toxicity screening, and discussions about the teenager's social interactions and mental health.