The question posed in the title of this post was asked and [partly] answered by the paper by Vincent Guinchat and colleagues  based on the analysis of 58 adolescents diagnosed with an autism spectrum disorder (ASD) and "hospitalized for severe challenging behaviors." Challenging behaviours, by the way, refers to a whole spectrum of presentations which doesn't just include aggressive or violent behaviours (see here). Indeed, I recently talked about irritability and autism (see here), which might also fall into this category under certain circumstances.
Guinchat and colleagues "aimed to assess risk factors associated with very acute behavioral crises in adolescents with ASD" by way of collecting various data on participants (both retrospectively and prospectively) including the severity of their presentation, the presence of "comorbid organic conditions" and assessing "predictors of Global Assessment Functioning Scale (GAFS) score and duration of hospitalization at discharge."
Results: well, an inpatient stay did seem to have a positive effect on participants as per the findings that: "During the inpatient stay... patients doubled on average their GAFS scores." A higher score translates as better outcome. Comorbid psychiatric conditions, known and unknown, was the most frequently cited reason for behavioural crises, with depressive episode and schizophrenia representing the known conditions cited most. Organic causes, including epilepsy and "painful medical conditions" followed in frequency, with environmental causes "including lack of treatment... and adjustment disorder" bringing up the rear. The authors also suggest that the severity of autism presentation (I draw back from using the idea of 'functioning') had a negative effect on GAFS scores at discharge. This point may also tie into some recent findings reported by Rattaz and colleagues  where symptom severity of autism might be a risk factor for the presence of self-injurious behaviours.
The authors conclude: "Challenging behaviors among adolescents with ASD may stem from diverse risk factors, including environmental problems, comorbid acute psychiatric conditions, or somatic illness such as epilepsy or acute pain. The management of these behavioral challenges requires a unified, multidisciplinary approach."
I know that some people might look at this data, shrug and say 'what did you expect', but I'm not one of them. Challenging behaviours can occur in relation to autism for all-manner of reasons but as per other discussions on this topic, one should never assume that challenging behaviours are just 'part and parcel' of a diagnosis of autism. They aren't, even if some of the signs and symptoms of autism may make a person more likely to present with such issues at certain times (including puberty).
I've talked before about some of the circumstances around challenging behaviours and autism as per the idea that pain and discomfort for example, might sometimes facilitate the presence of such issues (see here) particularly in the absence of functional language use. Indeed, a lack of communicative abilities (or rather suitable ways or avenues to communicate) can be a real obstacle to health equality more generally when it comes to autism (see here). Epilepsy or seizure-type disorders have also figured on the autism landscape (see here) and potentially contribute as an important factor when it comes to challenging behaviours for some . Ideas on the possibility of overlap between autism and conditions like certain types of depression and/or schizophrenia are gaining traction in recent times (see here and see here respectively) and again, suggest that 'diagnostic vigilance' are the keywords (see here).
To close: Take on Me by Harry Hill (and others)?
 Guinchat V. et al. Acute behavioral crises in psychiatric inpatients with autism spectrum disorder (ASD): Recognition of concomitant medical or non-ASD psychiatric conditions predicts enhanced improvement. Research in Developmental Disabilities. 2015; 38: 242-255.
 Rattaz C. et al. Symptom severity as a risk factor for self-injurious behaviours in adolescents with autism spectrum disorders. J Intellect Disabil Res. 2015 Jan 12.
 Ito M. et al. Subacute postictal aggression in patients with epilepsy. Epilepsy Behav. 2007 Jun;10(4):611-4.
Guinchat V, Cravero C, Diaz L, Périsse D, Xavier J, Amiet C, Gourfinkel-An I, Bodeau N, Wachtel L, Cohen D, & Consoli A (2015). Acute behavioral crises in psychiatric inpatients with autism spectrum disorder (ASD): Recognition of concomitant medical or non-ASD psychiatric conditions predicts enhanced improvement. Research in developmental disabilities, 38C, 242-255 PMID: 25575287