> Mental health issues are rife: approximately one-third of PhD students are at risk of having or developing a psychiatric disorder like depression.
The baseline percentage of the population which experience depression (and other mental illness) each year is known to be pretty high -- and highest in for people in their 20's. One third sounds fairly normal; at any rate, there is a burden here to show that this is an exceptional proportion.
> For instance, a PhD in Germany is supposed to take three years, according to university regulations, but most students need five years to complete one.
If you are starting from an undergraduate degree, you probably need at least two years to take the PhD intro classes. One year to start a research program might work in a subject like the author's where your papers are chats about social implications, but there are plenty of subjects where even the data collection is going to take longer than that.
> In the US, meanwhile, the average completion time for a PhD in education sciences surpasses 13 years.
These programs are dominated by people who are working teachers, working on PhDs part-time.
> One study found that for every 200 people who complete a PhD, only seven will get a permanent academic post and only one will become a professor.
Being a professor is only one possible goal and for some fields, it isn't even the primary one.