If someone is confused and disoriented (delirious), they can't be diagnosed with depression caused by another medical condition. But, if someone has a mental problem that affects their thinking and memory (neurocognitive disorder) and they also have depression, they can be diagnosed with both conditions. This is especially true if the depression is caused by the same thing that is causing the neurocognitive disorder and the symptoms of depression are explanatory of what's making the person sick.