Commodity prices during economic distress.

In the reading 30, section 5.3.1 (investment characteristics) it is stated that “in periods of financial and economic distress, commodity prices tend to rise, potentially providing valuable diversification benefits in such times”…however, few lines down it is stated that “commodity prices tend to decline during periods of weakness in the economy.”

I’m quite confused with this? Does anyone have an explanation for these contradicting statements?

Thanks in advance