The premise of this answer is that if math can be applied to accurately used for psychic phenomena than meta use of math can be applied accurately as well.
Psychoanalysis is a tricky subject. Unlike cognitive behavioural psychotherapy its goal isn't expressly to teach a new behavior but to find a source of a stimulus. If strands of thought based on rational movement and happenings were a line then the human condition certainly would be nonlinear because so much of what we do is a reflection of our training and associations from the past both conscious and subconscious. Though we know not the exact equation of consciousness we can accurately theorize that human intelligence is reflected in the artificial intelligences we have created. For instance some decisions can be mapped out as a proposition logical equation simular to a decision tree. Other decisions are based purely on instinct like neural networks and some come from recognizing and finding things that please and displease us like SVMs. Some of those equations would have random variables of course but much of what we do has been predetermined.
Something like this decision tree probabilities and truth values of situations contribute to the end result:
Other decisions can only be explained in terms of an equation of neurons firing and pleasure or goodness derived from each neuron like an SVM or Neural Net.
SVMs create linear and nonlinear discriminants which is a line that tells groups apart based on features. They can be quite complex in their ability to discriminate between pleasure and pain or classify an object.
Neural networks work based on several input senses which are weighted then ran through a function to determine if a pathway is activated.
The equation for sexual position of greatest preference might include things from past experiences, prejudices and preferences for pornography actors who were in that position, feelings associated with bending and flexing that way. Then as Freud acuaratly pointed out seeming random things from childhood that logically should be completely separate from sexuality but because we are connected individuals built systematically.
So yes using math especially those related to artificial intelligence, time series and propositional logic are useful methods in describing psychic phenomena. Simplifications of the aforementioned sometimes contributes to misunderstanding of how humans think but can be implemented in ways that facilitate understanding for those of less experience or education.