## 4 Discussion  
All patients had significant improvement in depression and balance after rehabilitation (Table 1). Overall, a decrease in TDQ score (\(p\) = 0.001) and an increase in BBS score (\(p\) < 0.001) were noted. We found the TDQ scores of patients in the yoga group were much lower than those in the control group after the intervention while the baseline TDQ scores were similar (Figure 2A). Only patients in the yoga group showed significant improvement in depression after the intervention which indicates yoga provided anti-depression effect. Because this was not a randomized trial, the baseline BBS score is much higher in the yoga group (with a better physical condition) compared to the control group even before intervention. BBS scores remained much higher after the intervention (Figure 2B). The reason may be that healthier people have higher intention to be volunteers for epidemiological research or a challenging task and have better survival rates than the general population, thereby producing bias referred to as the \"healthy volunteer effect\" [31]. Although both groups showed improvements in BBS scores (Figure 2B), the change of improvement in BBS was also significantly larger in the yoga group (\(p\) = 0.029). This finding indicates yoga still provided extra benefits compared to standard rehabilitation. We compared the differences in the effects of rehabilitation on both sexes (Table 2 and Figure 3). Overall, we found that depression was significantly improved equally (Figure 3A). Unlike depression, balance showed a significantly greater improvement in men generally than in women (\(p\) = 0.029) (Figure 3B). One possible explanation is that men have poorer flexibility than women due to a lack of hormones such as estrogen or relaxin. Relaxin is known for relaxing the tendons and joints in pregnancy and delivery in women [32]. Yoga has been proven to improve flexibility [33], and flexibility is related to balance [34]. It may be that women have better flexibility in the first place, so the improvement of flexibility and balance after yoga may not be as good as man. In other words, the mind factor (anti-depression) of yoga is similar for both sexes but the body factor (balance) is quite different with better improvements in men. The effect of brain lesion site is shown in Table 2 and Figure 3B. Only patients with left-sided brain lesions showed a significant improvement in depression (Figure 3C). This is probably due to left-sided brain lesion being associated with aphasia because the linguistic center is located the left brain while aphasia is highly associated with depression [35]. Yoga may lead to an improvement in aphasia [36]. Unlike depression, balance was uniformly improved in all subgroups of patients, despite of brain lesion side. These results are compatible with the brain structure whereby motor cortex is symmetrical, but the language center is located in the left brain [35]. Age is also an influencing factor. For patients younger than 60, depression (\(p\) = 0.032) and balance (\(p\) = 0.001) significantly improved. (Figure 3E). For older patients aged 60 or more, depression showed significant improvement (\(p\) = 0.015), and balance improved as well (\(p\) < 0.001) (Figure 3F). Therefore, rehabilitation is important for both young and older patients. Further analysis of factors associated with balance, we found the BBS score is much lower in the older group, as age is significantly inverse related to the balance (Figure 4). This could be because young patients have better neuroplasticity and muscle power [37]. Aging is a big contributor to poor balance (linear regression for age vs. baseline BBS score, \(p\) = 0.005, R\({}^{2}\) = 0.464; age vs. post-intervention BBS score, \(p\) = 0.006, R\({}^{2}\) = 0.456) (Figure 4A,B). Nonetheless, age is not associated with depression (Age vs. baseline TDQ score, \(p\) = 0.551; age vs. post-intervention BBS score, \(p\) = 0.439). Therefore, old age may not guarantee depression.