With the lack of detailed information about the effect of SUD among young adults on stroke characteristics and outcomes in Egypt, this study provided a better understanding of SUD-induced stroke in Egyptian young adults.

The co-existence of different comorbidities and SUD was investigated in this study; these comorbidities represent the main modifiable risk factors for stroke. It was noticed that most young stroke adults with different comorbidities developed stroke without SUD. This might denote that SUD, even without other comorbidities, is sufficient to be a risk factor for stroke.

Similar to our results, Chang, Münster [12] showed that anabolic androgenic steroids increased the risk of cerebral venous thrombosis. It is well-established that anabolic steroids cause an increase in prothrombin fragments and thrombin/antithrombin complexes, which leads to cerebral venous thrombosis [13, 14].

The present study showed that all cannabis abusers developed an arterial stroke predominantly of ischemic type (86%) involving the posterior circulation. This is in line with Middlekauff, Cooper [15], who found that cannabis-induced multifocal intracranial stenosis mostly involved the posterior circulation.

In contrast, the hemorrhagic type predominated over the ischemic stroke in heroin abusers. This could be explained by pyogenic arteritis or the rupture of mycotic aneurysms induced by heroin [16].

In light of the previous studies' agreement that cocaine-related stroke can be of any type and may happen in every brain region [16], the current study showed a significant preference for posterior circulation involvement among patients with cocaine use disorder. Potent cerebral vasospasm, cerebral vasculitis, and bradykinin-mediated endothelial dysfunction all have been demonstrated as consequences of cocaine abuse [17].

In 2016, a meta-analysis revealed that heavy alcohol consumption increases the risk for the hemorrhagic type, either ICH or SAH [18]. Regarding the ischemic events, alcohol-induced atrial fibrillation mainly contributes to cerebrovascular events [19], as the effects of alcohol on hemostatic and fibrinolytic factors are still doubtful [20]. However, we found no association between alcohol use disorder and any specific stroke type.

For tramadol, one of the most commonly abused substances by Egyptian youths [21, 22], data about its pathophysiological mechanisms of causing stroke is not settled yet [23]. Contrary to classic opioids, tramadol inhibits serotonin and norepinephrine reuptake, provoking autonomic hyperactivity like tachycardia, hypertension, and cardiac arrhythmia, which all may contribute to cerebrovascular events [24].

Only 74 patients in this study had received r-TPA during stroke management. Twenty percent of abusers received r-TPA, whereas 40% of the non-abusers were eligible for r-TPA, which poses a question of whether substance abuse might affect the issues related to the eligibility for the usage of r-TPA in the treatment protocol. However, no statistically significant differences in stroke outcome after IV thrombolysis between different illicit substances.

Mortality among young stroke patients was estimated to be 4.5% at 30-day follow-up by Rutten-Jacobs, Arntz [25]. Yet, the mortality rate reported by the current study (3.5%) was relatively lower than the previously mentioned study. In general, high mortality outcomes among SUD patients might be attributed to the adverse cardiac effects of illicit substances [26]. Mahtta, Ramsey [27] reported an increased risk of premature atherosclerotic cardiovascular diseases induced by all substances included in the current study. However, in the present study, heroin was the only substance associated with significantly higher mortality, which might be attributed to the predominantly hemorrhagic stroke type associated with heroin use disorder. It is well-known that intracerebral hemorrhage has a higher case fatality rate than ischemic stroke [28, 29].

The present study observed poor functional outcomes among patients with alcohol, heroin, and cocaine use disorders, using the Modified Rankin Scale after 1 month of stroke onset. It is well-established that baseline NIHSS strongly predicts functional outcomes [30–32]. As previously reported in this study, alcohol, heroin, and cocaine were significantly associated with higher NIHSS scores at the onset; these substances would be expected to be significantly associated with a poor outcome. These findings disagree with Sheikh Andalibi, Rezaei Ardani [33], who did not find a significant difference in functional dependency between patients with SUD versus non-SUD.

This present study had some limitations that should be mentioned. Some stroke patients refrained from seeking emergency treatment at hospitals for fear of infection during the COVID-19 pandemic; this influenced the number of young stroke cases collected in this study. Secondly, the study followed the stroke outcome only for 1 month, missing the opportunity to assess the outcome (recurrence, disability, and mortality) for extended periods post-stroke, hoping that future research will overcome these limitations.