dr. von waldner conducts research on depression. his hypothesis is that depression results from maladaptive thought patterns. from which perspective is von waldner working?

The answer is "cognitive perspective".

There are various psychology perspectives, these perspectives include diverse clarifications for human conduct.  

One of these psychology perspectives is the cognitive perspective.  

The cognitive perspective is concerned about comprehension mental procedures, for example, memory, discernment, considering, and critical thinking, and how they might be identified with conduct.