I get this question frequently from people who are anxious and have panic attacks. While CBT is effective and attempts to find anxiety-provoking and maladaptive thoughts, people who are anxious can’t always find those triggering thoughts, and just have a panic attack out of the blue, so it seems.
The issue with people who have anxiety is that their anxiety circuits (based on the amygdala) are already revved up and hyperactive, and the malfunctioning occurs at different frequencies and intensities depending on the type of anxiety. So when you have panic disorder, the malfunctioning is catastrophic and unexpectedly intermittent, while in generalized anxiety disorder, the malfunctioning is not as severe but constant. In social anxiety disorder the malfunctioning is catastrophic and expectedly intermittent, while in PTSD it is traumatic and catastrophic. In OCD, the malfunctioning is repetitive and chronic.
So the neurobiology of someone with anxiety is that their anxiety circuits are already revved up and malfunctioning, albeit at different frequencies and intensities, depending on the type of anxiety.
So if you are not able to find the triggering thoughts to your anxiety, then you may need other ways besides CBT to reduce your overall anxiety levels, as your anxiety circuits are malfunctioning as described above. You may need to resort to different, such as relaxation, meditation, yoga, exercise, prescription medication, or natural anxiety treatments. Then when your overall anxiety levels are reduced, you may be able to discern those anxiety-provoking thoughts that have been masked by those severe anxiety symptoms you experienced previously.